Online Etymology Dictionary

lumpy (adj.): 1707, "abounding in lumps," from lump (n.) + -y (2). In early 19c. slang, "drunk." Among sailors, of the sea when forming small waves in rough water, from 1857. Related: Lumpiness.
luna (n.): late 14c. "the moon," especially as personified in a Roman goddess answering to Greek Selene; also an alchemical name for "silver;" from Latin luna "moon, goddess of the moon," from PIE *leuksna- (source also of Old Church Slavonic luna "moon," Old Prussian lauxnos "stars," Middle Irish luan "light, moon"), suffixed form of root *leuk- "light, brightness." The luna moth (1841, American English) so called for the crescent-shaped eye-spots on its wings.
lunacy (n.): 1540s, "condition of being a lunatic," formed irregularly in English from lunatic (q.v.) + -cy. Originally in reference to intermittent periods of insanity, such as were believed to be triggered by the moon's cycle. The Old English equivalent was monaðseocnes "month-sickness." In later legal use, any unsoundness of mind sufficient to render one incapable of civil transactions or management of one's affairs. Weakened figurative sense "act of madness or folly" is from 1580s.
lunar (adj.): early 15c., "crescent-shaped;" 1620s, "pertaining to the moon," from Old French lunaire (15c.), from Latin lunaris "of the moon," from luna "moon" (see luna).
Lunarian (n.): 1708, "moon-man, inhabitant of the moon;" see lunar + -ian. Also "expert on or student of lunar phenomena" (1817).
lunate (adj.): "crescent-shaped," 1777, from Latin lunatus "half-moon shaped," from luna "moon" (see luna).
lunatic (n.): "lunatic person," late 14c., from lunatic (adj.). Originally one with lucid intervals; later, in legal use, a general term for a person of unsound mind.
lunatic (adj.): late 13c., "affected with periodic insanity dependent on the changes of the moon," from Old French lunatique "insane," or directly from Late Latin lunaticus "moon-struck," from Latin luna "moon" (see luna).

Compare Old English monseoc "lunatic," literally "moon-sick;" Middle High German lune "humor, temper, mood, whim, fancy" (German Laune), from Latin luna. Compare also New Testament Greek seleniazomai "be epileptic," from selene "moon." Lunatic fringe (1913) apparently was coined by U.S. politician Theodore Roosevelt.
Then, among the wise and high-minded people who in self-respecting and genuine fashion strive earnestly for peace, there are foolish fanatics always to be found in such a movement and always discrediting it -- the men who form the lunatic fringe in all reform movements. [Theodore Roosevelt, autobiography, 1913].
Earlier it was a term for a type of hairstyle worn over the forehead (1877). Lunatic soup (1933) was Australian slang for "alcoholic drink."
lunation (n.): "time from one new moon to the next," late 14c., from Medieval Latin lunationem, from Latin luna "moon" (see luna).
lunch (n.): "mid-day repast, small meal between breakfast and dinner," 1786, a shortened form of luncheon (q.v.) in this sense (1650s), which is of uncertain origin; it appears to be identical with an older word meaning "thick piece, hunk" (1570s), which perhaps evolved from lump (n.) [OED]. There also was a contemporary nuncheon "light mid-day meal," from noon + Middle English schench "drink." Old English had nonmete "afternoon meal," literally "noon-meat." The verb meaning "to take to lunch" (said to be from the noun) also is attested from 1786:
PRATTLE. I always to be ſure, makes a point to keep up the dignity of the family I lives in. Wou'd you take a more ſolid refreſhment?--Have you lunch'd, Mr. Bribe?
BRIBE. Lunch'd O dear! Permit me, my dear Mrs. Prattle, to refreſh my sponge, upon the honey dew that clings to your raviſhing pouters. O! Mrs. Prattle, this ſhall be my lunch. (kiſſes)
["The Mode," in William Davies' "Plays Written for a Private Theatre," London, 1786]
As late as 1817 the only definition of lunch (n.) in Webster's is "a large piece of food," but this is now obsolete. OED says in 1820s the word "was regarded either as a vulgarism or as a fashionable affectation." Related: Lunched; lunching. Lunch money is attested from 1868. Lunch-time is from 1821; lunch hour is from 1840; lunch-break is from 1960. Slang phrase out to lunch "insane, stupid, clueless" first recorded 1955, on notion of being "not there."
lunch (v.): 1786, from lunch (n.). Related: Lunched; lunching.
lunch-box (n.): 1864, from lunch (n.) + box (n.1).
lunch-counter (n.): "long, elevated table where customers eat standing or sitting on high stools," American English; see lunch (n.) + counter (n.).
lunch-pail (n.): such as working men used to carry their lunches to job sites, 1891, from lunch (n.) + pail (n.). As an adjective, indicating working-class men or values, by 1990s, also lunch-bucket.
luncheon (n.): "light repast between mealtimes," 1650s (lunching; spelling luncheon by 1706); earlier "thick piece, hunk (of bread)," 1570s (luncheon), which is of uncertain origin. Perhaps it is based on northern English dialectal lunch "hunk of bread or cheese" (1580s; said to be probably from Spanish lonja "a slice," literally "loin"), blended with or influenced by nuncheon (Middle English nonechenche, mid-14c.) "light mid-day meal," from none "noon" (see noon) + schench "drink," from Old English scenc, from scencan "pour out."

Despite the form lunching in the 1650s source OED discounts that it possibly could be from lunch (v.), which is first attested more than a century later. It suggests perhaps an analogy with truncheon, etc., or to simulate a French origin. Especially in reference to an early afternoon meal eaten by those who have a noontime dinner.
luncheonette (n.): type of restaurant, 1906, American English, from luncheon + diminutive ending -ette.
lunchmeat (n.): also lunch-meat, 1931, from lunch (n.) + meat (n.).
lune (n.): figure formed by two arcs of circles, anything in the shape of a crescent or half-moon, 1704, from Latin luna "moon; crescent-shaped badge" (see luna).
lunette (n.): 1570s, "semi-circular partial horseshoe," from Middle French lunette (13c.), literally "little moon," diminutive of lune "moon," from Latin luna (see luna). Later applied to a wide range of objects and ornamentations resembling more or less a crescent moon.
lung (n.): human or animal respiratory organ, c. 1300, from Old English lungen (plural), from Proto-Germanic *lungw- (source also of Old Norse lunge, Old Frisian lungen, Middle Dutch longhe, Dutch long, Old High German lungun, German lunge "lung"), literally "the light organ," from PIE root *legwh- "not heavy, having little weight" (source also of Russian lëgkij, Polish lekki "light;" Russian lëgkoje "lung").

So called perhaps because in a cook pot lungs of a slaughtered animal float, while the heart, liver, etc., do not. Compare Portuguese leve "lung," from Latin levis "light;" Irish scaman "lungs," from scaman "light;" Welsh ysgyfaint "lungs," from ysgafn "light." See also lights, pulmonary. Lung cancer is attested from 1882. Lung-power "strength of voice" is from 1900.
lung-fish (n.): also lungfish, 1883, from lung (n.) + fish (n.).
lunge (v.): "to thrust," as in fencing, 1735 (implied in lunged), from lunge (n.). Sense of "make a sudden forward rush" is from 1821. Related: Lunging.
lunge (n.): 1735, "a thrust with a sword," originally a fencing term, shortened from allonge, from French allonger "to extend, thrust," from Old French alongier "to lengthen, make long," from à "to" + Old French long, from Latin longus "long" (see long (adj.)).
luni-: word-forming element meaning "of the moon, of the moon and," from Latin luna "moon" (see luna).
lunk (n.): "solid, slow-witted person," 1867, American English colloquial, shortened from lunkhead (1852), which is possibly an altered form of lump (n.) + head (n.)
Lupercalia (n.): Roman festival held Feb. 15 in honor of Lupercus a god (identified with Lycean Pan, hence regarded as a protective divinity of shepherds) who had a grotto at the foot of the Palatine Hill, from Latin Lupercalia (plural), from Lupercalis "pertaining to Lupercus," whose name derives from lupus "wolf" (see wolf (n.)). The ceremony is regarded as dating from distant antiquity. Related: Lupercalian.
lupin (n.): also lupine, flowering plant of the genus lupinus, late 14c., from Latin lupinus, the name of the plant, a noun use of an adjective meaning "of a wolf," from lupus "wolf" (see wolf (n.)). The reason for the name is unclear; perhaps the plant was so called because of a belief that it was harmful to soil (compare lupus in the "wasting disease" sense), but in modern Europe it was regarded as useful and valued for improving sandy soil. In Portugal it was used to choke out weeds.
lupine (adj.): "wolf-like," 1650s, from French lupin "wolf-like; vicious, ferocious," from Latin lupinus "of the wolf" (source also of Spanish and Italian lupino), from lupus "wolf" (see wolf (n.)).
lupus (n.): late 14c., used of several diseases that cause ulcerations of the skin, from Medieval Latin lupus, from Latin lupus "wolf" (see wolf (n.)), apparently because it "devours" the affected part. As the name of a southern constellation representing a wolf, by 1706.
lurch (v.): 1821, "to roll or sway suddenly to one side," from lurch (n.1). Meaning "walk with an uneven gait" is from 1851. Related: Lurched; lurching.
lurch (n.1): "sudden pitch to one side," 1784, from earlier lee-larches (1765), a nautical term for "the sudden roll which a ship makes to lee-ward in a high sea, when a large wave strikes her, and bears her weather-side violently up, which depresses the other in proportion" ["Complete Dictionary of Arts and Sciences," London 1765]. This is perhaps from French lacher "to let go," from Latin laxus (see lax).
When a Ship is brought by the Lee, it is commonly occaſsioned by a large Sea, and by the Neglect of the Helm's-man. When the Wind is two or three Points on the Quarter, the Ship taking a Lurch, brings the Wind on the other Side, and lays the Sails all dead to the Maſt; as the Yards are braced up, ſhe then having no Way, and the Helm being of no Service, I would therefore brace about the Head ſails ſharp the other Way .... [John Hamilton Moore, Practical Navigator, 8th ed., 1784]
lurch (n.2): "predicament," 1580s, from Middle English lurch (v.) "to beat in a game of skill (often by a great many points)," mid-14c. (implied in lurching), probably literally "to make a complete victory in lorche," an old game akin to backgammon, with a name of uncertain origin. Perhaps it is related to Middle English lurken, lorken "to lie hidden, lie in ambush" (Middle English Dictionary; see lurk), or it may be from Old French lourche, from Middle High German lurz "left," also "wrong" [OED]. The immediate source of the transferred use in leave in the lurch "leave suddenly and unexpectedly in an embarrassing predicament" (1590s) would be cribbage.
lure (v.): late 14c., "attract (a hawk) by casting a lure or decoy," also of persons, "to allure, entice, tempt," from lure (n.). Related: Lured; luring; lurement.
lure (n.): early 14c., "something which allures or entices, an attraction" (a figurative use), originally the name of a device for recalling a hawk, from Anglo-French lure, Old French loirre "device used to recall hawks, lure," from Frankish *lothr or some other Germanic source, from Proto-Germanic *lothran "to call" (source also of Middle High German luoder, Middle Low German loder "lure, bait," German Luder "lure, deceit, bait;" also Old English laþian "to call, invite," German laden "invite, summon").

The original lure was a bunch of feathers, arranged so as to resemble a bird, on a long cord, from which the hawk was fed during its training. Used of means of alluring other animals (especially fish) from c. 1700. Technically, bait (n.) is something the animal could eat; lure is a more general term. Also in 15c. a collective word for a group of young women (as a c. 1400 document has it, "A lure of ffaukones & damezelez").
lurid (adj.): 1650s, "pale, wan," from Latin luridus "pale yellow, ghastly, the color of bruises," a word of uncertain origin and etymology, perhaps cognate with Greek khloros "pale green, greenish-yellow" (see Chloe), or connected to Latin lividus (see livid).

It has more to do with the interplay of light and darkness than it does with color. It suggests a combination of light and gloom; "Said, e.g. of the sickly pallor of the skin in disease, or of the aspect of things when the sky is overcast" [OED]; "having the character of a light which does not show the colors of objects" [Century Dictionary]. Meaning "glowing in the darkness" is from 1727 ("of the color or appearance of dull smoky flames" - Century Dictionary]. In scientific use (1767) "of a dingy brown or yellowish-brown color" [OED]. The figurative sense of "sensational" is first attested 1850, via the notion of "ominous" (if from the flames sense) or "ghastly" (if from the older sense). Related: Luridly.
lurk (v.): c. 1300, lurken "to hide, lie hidden," probably from Scandinavian (compare dialectal Norwegian lurka "to sneak away," dialectal Swedish lurka "to be slow in one's work"), perhaps ultimately related to Middle English luren "to frown, lurk" (see lower (v.2)). From late 14c. as "move about secretly;" also "escape observation." Related: Lurked; lurking.
lurker (n.): "one who keeps out of sight," early 14c., agent noun from lurk (v.). In the internet sense by 1990.
Lusatian: 1550s, from Medieval Latin Lusatia.
luscious (adj.): late 15c., according to Middle English Dictionary a variant of Middle English licius "delicious" (c. 1400), which is a shortening of delicious, with the variant form perhaps influenced by Old French luxure, lusure. But OED 2nd ed. and Century Dictionary are against all this and the former considers it "of obscure origin" while the latter suggests lusty with a pseudo-Latin ending. John Palsgrave, the 16c. grammarian, spelled it lussyouse. Related: Lusciously; lusciousness.
lush (n.): "drunkard," 1890, from earlier slang meaning "liquor" (1790, especially in phrase lush ken "alehouse"), of obscure origin; perhaps a humorous use of lush (adj.) or from a word in Romany or Shelta (tinkers' jargon). It also was a verb, "to drink heavily" (1811).
LUSHEY. Drunk. The rolling kiddeys had a spree, and got bloody lushey; the dashing lads went on a party of pleasure, and got very drunk. ["Dictionary of Buckish Slang, University Wit, and Pickpocket Eloquence," London, 1811]
Hence also Lushington humorous generic name for a tippler (1823).
lush (adj.): mid-15c., "lax, flaccid, soft, tender" (obsolete or dialectal), from Old French lasche "soft, loose, slack, negligent, cowardly," from laschier "loosen," from Late Latin laxicare "become shaky," related to Latin laxare "loosen," from laxus "loose" (from PIE root *sleg- "be slack, be languid"). The main modern sense of the word, with reference to plant life, "luxuriant in growth," is first attested c. 1600, in Shakespeare. Related: Lushly; lushness.
Lusitania: Latin name of a region roughly corresponding to modern Portugal and part of Spain; in modern use, allusive or poetic for "Portugal." The Cunard ocean liner (sister ship of the Mauretania and Aquitania, also named after Roman Atlantic coastal provinces) was launched in 1906, torpedoed and sunk by German submarine U-20 on May 7, 1915. Related: Lusitanian.
lusory (adj.): "playful," 1650s, from Latin lusorius "belonging to a player," from lusor "player," from stem of ludere "to play" (see ludicrous). Related: Lusorious (1610s).
lust (v.): c. 1200, "to wish, to desire eagerly," from lust (n.), absorbing or replacing the older verb, Old English lystan (see list (v.4)). In Middle English also "to please, delight." Sense of "to have an intense, especially sexual, desire (for or after)" is first attested 1520s in biblical use. Related: Lusted; lusting.
lust (n.): Old English lust "desire, appetite; inclination, pleasure; sensuous appetite," from Proto-Germanic *lustuz (source also of Old Saxon, Old Frisian, Dutch lust, German Lust, Old Norse lyst, Gothic lustus "pleasure, desire, lust"), abstract noun from PIE *las- "to be eager, wanton, or unruly" (source also of Latin lascivus "wanton, playful, lustful;" see lascivious).

In Middle English, "any source of pleasure or delight," also "an appetite," also "a liking for a person," also "fertility" (of soil). Specific and pejorative sense of "sinful sexual desire, degrading animal passion" (now the main meaning) developed in late Old English from the word's use in Bible translations (such as lusts of the flesh to render Latin concupiscentia carnis in I John ii:16); the cognate words in other Germanic languages tend to mean simply "pleasure." Masculine in Old English, feminine in modern German.
luster (n.2): "one who feels intense longing desire," 1590s, agent noun from lust (v.).
luster (n.1): "gloss, radiance, quality of shining by reflecting light," 1520s, from Middle French lustre "gloss, radiance" (14c.), common Romanic (cognates: Spanish and Portuguese lustre, Rumanian lustru, Italian lustro "splendor, brilliancy"), a noun ultimately from Latin lustrare "spread light over, brighten, illumine," which is related to lustrum "purification," from PIE *leuk-stro-, suffixed form of root *leuk- "light, brightness."

Especially "quality of glossiness or radiance in a textile material or fabric." Figurative meaning "radiant beauty" is from c. 1600; that of "splendor, renown" is from 1550s. Luster-ware is from 1825.
lusterless (adj.): 1805, from lustre + -less.
lustful (adj.): Old English lustful "wishful, desirous, having an eager desire;" see lust (n.) + -ful. Specifically of immoderate sexual desire from 1570s. Related: Lustfully; lustfulness. Formerly also "vigorous" (1560s), a sense now given to lusty. Middle English also had lustsome, which was used in a sense of "voluptuous, lustful" from c. 1400, and lustly "pleasant," also "lustful." Old English had lustbære "desirable, pleasant, cheerful, joyous."
lustgarden (n.): 1580s, translation or partial translation of German Lust-garten, Dutch lustgaard "pleasure garden;" see lust (n.) + garden (n.).