learning (n.) Look up learning at Dictionary.com
Old English leornung "learning, study," from leornian (see learn). Learning curve attested by 1907.
lease (n.) Look up lease at Dictionary.com
late 14c., "legal contract conveying property, usually for a fixed period of time and with a fixed compensation," from Anglo-French les (late 13c.), from lesser "to let, let go," from Old French laissier "to let, allow, permit; bequeath, leave," from Latin laxare "loosen, open, make wide," from laxus "loose" (see lax). Medial -x- in Latin tends to become -ss- or -s- in French (compare cuisse from coxa). Modern French equivalent legs is altered by erroneous derivation from Latin legatum "bequest, legacy."
lease (v.) Look up lease at Dictionary.com
late 15c., "to take a lease," from Anglo-French lesser, Old French laissier "to let, leave" (see lease (n.). Related: Leased; leasing. Lessor, lessee in contract language preserves the Anglo-French form.
leash (v.) Look up leash at Dictionary.com
"to attach to or with a leash," 1590s, from leash (n.). Related: Leashed; leashing.
leash (n.) Look up leash at Dictionary.com
"thong for holding a dog or hound," c. 1300, from Old French laisse "hound's leash," from laissier "loosen," from Latin laxare, from laxus "loose" (see lax). Figurative sense attested from early 15c. The meaning "a set of three" is from early 14c., originally in sporting language.
least (adj.) Look up least at Dictionary.com
Old English læst, earlier læsest "smallest" (superlative of lytel "small"), from Proto-Germanic superlative *laisistaz (see less). Qualifying phrase at least is Middle English æt læstan. As a noun, from early 12c.; as an adverb, c. 1200.
leastways Look up leastways at Dictionary.com
1825, colloquial, from least + way (n.). Regarded as vulgar, but simply a one-word form of Chaucer's leest weye (late 14c.).
leather (n.) Look up leather at Dictionary.com
Old English leðer (in compounds only) "hide, skin, leather," from Proto-Germanic *lethran (cognates: Old Norse leðr, Old Frisian lether, Old Saxon lethar, Middle Dutch, Dutch leder, Old High German ledar, German leder), from PIE *letro- "leather" (cognates: Old Irish lethar, Welsh lledr, Breton lezr). As an adjective from early 14c.; it acquired a secondary sense of "sado-masochistic" 1980s, having achieved that status in homosexual jargon in the 1970s.
leathern (adj.) Look up leathern at Dictionary.com
Old English leðren; see leather + -en (2).
leatherneck (n.) Look up leatherneck at Dictionary.com
"U.S. Marine," 1914, Navy slang, from leather + neck (n.). So called for the leather collars of their early uniforms; earlier in British use (1890) as a sailor's term for a soldier.
leathery (adj.) Look up leathery at Dictionary.com
1550s, from leather + -y (2). Related: Leatheriness.
leave (v.) Look up leave at Dictionary.com
Old English læfan "to let remain; remain; have left; bequeath," from Proto-Germanic *laibijan (cognates: Old Frisian leva "to leave," Old Saxon farlebid "left over"), causative of *liban "remain," (source of Old English belifan, German bleiben, Gothic bileiban "to remain"), from root *laf- "remnant, what remains," from PIE *leip- "to stick, adhere;" also "fat."

The Germanic root has only the sense "remain, continue," which also is in Greek lipares "persevering, importunate." But this usually is regarded as a development from the primary PIE sense of "adhere, be sticky" (compare Lithuanian lipti, Old Church Slavonic lipet "to adhere," Greek lipos "grease," Sanskrit rip-/lip- "to smear, adhere to." Seemingly contradictory meaning of "depart" (early 13c.) comes from notion of "to leave behind" (as in to leave the earth "to die;" to leave the field "retreat").
leave (n.) Look up leave at Dictionary.com
"permission," Old English leafe "leave, permission, license," dative and accusative of leaf "permission," from Proto-Germanic *lauba (cognates: Old Norse leyfi "permission," Old Saxon orlof, Old Frisian orlof, German Urlaub "leave of absence"), from PIE *leubh- "to care, desire, love, approve" (see love (n.)). Cognate with Old English lief "dear," the original idea being "approval resulting from pleasure." Compare love, believe. In military sense, it is attested from 1771.
leave-taking (n.) Look up leave-taking at Dictionary.com
late 14c., from leave (n.) + present participle of take (v.).
leaved (adj.) Look up leaved at Dictionary.com
"having leaves," past participle adjective from verb leave "to put forth leaves," mid-13c., from leaf (n.).
leaven (n.) Look up leaven at Dictionary.com
mid-14c., from Old French levain "leaven, sourdough" (12c.), from Latin levamen "alleviation, mitigation," but used in Vulgar Latin in its literal sense of "a means of lifting, something that raises," from levare "to raise" (see lever). Figurative use from late 14c.
leaven (v.) Look up leaven at Dictionary.com
c. 1400, from leaven (n.). Related: Leavened; leavening.
Lebanese Look up Lebanese at Dictionary.com
1860, from Lebanon + -ese.
Lebanon Look up Lebanon at Dictionary.com
name of a nation in western Asia, from Semitic root l-b-n "white," probably in reference to snow-capped peaks, or possibly to chalk or limestone cliffs. The Greek name of the island Lemnos is of Phoenician origin and from the same root.
lebensraum (n.) Look up lebensraum at Dictionary.com
"territory needed for a nation's or people's natural development," 1905, from German genitive of leben "life" (see life) + raum "space" (see room (n.)).
lecanomancy (n.) Look up lecanomancy at Dictionary.com
"divination by inspection of water in a basin," c. 1600, from Latinized form of Greek lekane "dish-pan" + -mancy.
lech (n.1) Look up lech at Dictionary.com
"Celtic monumental stone," 1768, from Welsh llech, cognate with Gaelic and Irish leac (see cromlech).
lech (n.2) Look up lech at Dictionary.com
"yen, strong desire" (especially sexual), 1796, variant of letch. Meaning "a lecher" is by 1943.
lecher (n.) Look up lecher at Dictionary.com
"man given to excessive sexual indulgence," late 12c., from Old French lecheor (Modern French lécheur) "one living a life of debauchery," especially "one given to sexual indulgence," literally "licker," agent noun from lechier "to lick, to live in debauchery or gluttony," from Frankish *likkon or some other Germanic source, from Proto-Germanic *likkojan "to lick" or some other Germanic source (see lick). The Old French feminine form was lechiere. Middle English, meanwhile, had lickestre "female who licks;" figuratively "a pleasure seeker," literally "lickster."
lecherous (adj.) Look up lecherous at Dictionary.com
c. 1300, probably from lecher + -ous; or else from rare Old French lecheros. Related: Lecherously; lecherousness.
lechery (n.) Look up lechery at Dictionary.com
c. 1200, from Old French lecherie "impertinence, deceit," from lecheor (see lecher).
The priests had excellent cause to forbid us lechery: this injunction, by reserving to them acquaintance with and absolution for these private sins, gave them an incredible ascendancy over women, and opened up to them a career of lubricity whose scope knew no limits. [Marquis de Sade, "Philosophy in the Bedroom"]
lecithin (n.) Look up lecithin at Dictionary.com
fatty substance found in the yolks of eggs (among other places), 1861, from French lécithine (coined 1850 by N.T. Gobley), from Greek lekithos "egg yolk," + chemical suffix -ine (2). Greek lekithos is of unknown origin.
lectern (n.) Look up lectern at Dictionary.com
early 14c., lettorne, lettron, from Old French letron, from Medieval Latin lectrinum, from Late Latin lectrum "lectern," from root of Latin legere "to read" (see lecture (n.)). Half-re-Latinized in English in 15c.
lectio difficilior Look up lectio difficilior at Dictionary.com
Latin, literally "harder reading," from phrase maxim difficilior lectio potior. In textual reconstruction (of the Bible, etc.) the idea that, of two alternative manuscript readings, the one whose meaning is less obvious is less likely to be a copyist's alteration, and therefore should be given precedence.
lection (n.) Look up lection at Dictionary.com
1530s, from Old French lection, from Latin lectionem (nominative lectio), noun of action from past participle stem of legere "to read" (see lecture (n.)).
lector (n.) Look up lector at Dictionary.com
late 14c., "reader, a cleric in one of the minor orders," from Late Latin lector "reader," agent noun from Latin legere "to read" (see lecture (n.)). Related: Lectorship.
lecture (n.) Look up lecture at Dictionary.com
late 14c., "action of reading, that which is read," from Medieval Latin lectura "a reading, lecture," from Latin lectus, past participle of legere "to read," originally "to gather, collect, pick out, choose" (compare election), from PIE *leg- (1) "to pick together, gather, collect" (cognates: Greek legein "to say, tell, speak, declare," originally, in Homer, "to pick out, select, collect, enumerate;" lexis "speech, diction;" logos "word, speech, thought, account;" Latin lignum "wood, firewood," literally "that which is gathered").

To read is to "pick out words." Meaning "action of reading (a lesson) aloud" is from 1520s. That of "a discourse on a given subject before an audience for purposes of instruction" is from 1530s.
lecture (v.) Look up lecture at Dictionary.com
1580s, from lecture (n.). Meaning "to address severely and at length" is from 1706. Related: Lectured; lecturing.
lecturer (n.) Look up lecturer at Dictionary.com
1580s, agent noun from lecture (v.).
LED (n.) Look up LED at Dictionary.com
1968, initialism (acronym) from light-emitting diode.
led Look up led at Dictionary.com
past tense and past participle of lead (v.).
lede (n.) Look up lede at Dictionary.com
by 1965, alternative spelling of lead (n.2) in the newspaper journalism sense (see lead (v.)), to distinguish this sense from other possible meanings of the written word, perhaps especially the molten lead (n.1) used in typesetting machines.
lederhosen (n.) Look up lederhosen at Dictionary.com
leather shorts worn in Alpine regions, 1937, German, literally "leather trousers" (see leather and hose). Old English had cognate leðerhose. German hosen displaced Old High German bruch, from the basic Germanic word for "trousers" (see breeches).
ledge (n.) Look up ledge at Dictionary.com
late 13c., "crossbar on a door," perhaps from Middle English verb leggen "to place, lay" (see lay (v.)). Sense of "narrow shelf" is first recorded 1550s; "shelf-like projection of rock" is from 1550s.
ledger (n.) Look up ledger at Dictionary.com
"account book," c. 1400, from leggen "to place, lay" (see lay (v.)). Originally a book that lies permanently in a place (especially a large copy of a breviary in a church). Sense of "book of accounts" is first attested 1580s, short for ledger-book (1550s).
lee (n.) Look up lee at Dictionary.com
Old English hleo "shelter, cover, defense, protection," from Proto-Germanic *khlewaz (cognates: Old Norse hle, Danish , Old Saxon hleo, Dutch lij "lee, shelter"). No known cognates outside Germanic; original sense uncertain and might have been "warm" (compare German lau "tepid," Old Norse hly "shelter, warmth"), which might link it to PIE *kele- (1) "warm." Nautical sense "that part of the hemisphere to which the wind is directed" (c. 1400) is from the notion of the side of the ship opposite that which receives the wind as the sheltered side. As an adjective, 1510s, from the noun.
Lee-Enfield Look up Lee-Enfield at Dictionary.com
1902, named for J.P. Lee (1831-1904), U.S. designer of bolt action + Enfield (q.v.).
leech (n.1) Look up leech at Dictionary.com
"bloodsucking aquatic worm," from Old English læce (Kentish lyce), of unknown origin (with a cognate in Middle Dutch lake). Commonly regarded as a transferred use of leech (n.2), but the Old English forms suggest a distinct word, which has been assimilated to leech (n.2) by folk etymology [see OED]. Figuratively applied to human parasites since 1784.
leech (n.2) Look up leech at Dictionary.com
obsolete for "physician," from Old English læce, probably from Old Danish læke, from Proto-Germanic *lekjaz "enchanter, one who speaks magic words; healer, physician" (cognates: Old Frisian letza, Old Saxon laki, Old Norse læknir, Old High German lahhi, Gothic lekeis "physician"), literally "one who counsels," perhaps connected with a root found in Celtic (compare Irish liaig "charmer, exorcist, physician") and Slavic (compare Serbo-Croatian lijekar, Polish lekarz), from PIE *lep-agi "conjurer," from root *leg- "to collect," with derivatives meaning "to speak" (see lecture (n.)).

For sense development, compare Old Church Slavonic baliji "doctor," originally "conjurer," related to Serbo-Croatian bajati "enchant, conjure;" Old Church Slavonic vrači, Russian vrač "doctor," related to Serbo-Croatian vrač "sorcerer, fortune-teller." The form merged with leech (n.1) in Middle English, apparently by folk etymology. In 17c., leech usually was applied only to veterinary practitioners. The fourth finger of the hand, in Old English, was læcfinger, translating Latin digitus medicus, Greek daktylus iatrikos, supposedly because a vein from that finger stretches straight to the heart.
leechcraft (n.) Look up leechcraft at Dictionary.com
"art of healing," Old English læcecræft; see leech (2) + craft (n.).
leek (n.) Look up leek at Dictionary.com
culinary herb, Old English læc (Mercian), leac (West Saxon) "leek, onion, garlic," from Proto-Germanic *lauka- (cognates: Old Norse laukr "leek, garlic," Danish løg, Swedish lök "onion," Old Saxon lok "leek," Middle Dutch looc, Dutch look "leek, garlic," Old High German louh, German Lauch "leek"). No known cognates; Finnish laukka, Russian luk-, Old Church Slavonic luku are borrowed from Germanic.
leer (v.) Look up leer at Dictionary.com
"to look obliquely" (now usually implying "with a lustful or malicious intent"), 1520s, probably from Middle English noun ler "cheek," from Old English hleor "the cheek, the face," from Proto-Germanic *khleuzas "near the ear," from *kleuso- "ear," from PIE root *kleu- "to hear" (see listen). The notion is probably of "looking askance" (compare figurative development of cheek). Related: Leered; leering.
leer (n.) Look up leer at Dictionary.com
1590s, from leer (v).
leery (adj.) Look up leery at Dictionary.com
"untrusting, suspicious, alert," 1718, originally slang, with -y (2), and perhaps from dialectal lere "learning, knowledge" (see lore), or from leer (v.) in some now-obscure sense. OED suggests connection with archaic leer (adj.) "empty, useless," a general Germanic word (cognate with German leer, Dutch laar), of unknown origin.
lees (n.) Look up lees at Dictionary.com
late 14c., from Old French lies, plural of lie "sediment," probably from Celtic (compare Old Irish lige "a bed, a lying"), from PIE root *legh- "to lie" (see lie (v.2)).