letter (v.)
"to write in letters," 1660s, from letter (n.1). Earlier it meant "to instruct" (mid-15c.). Related: Lettered; lettering.
letter (n.2)
"one who lets" in any sense, c.1400, agent noun from let (v.).
lettered (adj.)
"literate," c.1300, from letter (n.). Meaning "inscribed" is from 1660s.
letterhead (n.)
1868, short for letterheading (1867); from letter (n.1) + head (n.). So called because it was printed at the "head" of the piece of paper.
lettering (n.)
1640s, "act of writing;" 1811 as "act of putting letters on something," verbal noun from letter (v.).
letters (n.)
"the profession of authorship or literature," mid-13c., from plural of letter (n.).
lettuce (n.)
late 13c., probably from Old French laitues, plural of laitue "lettuce," from Latin lactuca "lettuce," from lac (genitive lactis) "milk" (see lactation); so called for the milky juice of the plant.
leu (n.)
monetary unit of Romania, introduced 1867, literally "lion." Monetary names in the Balkans often translate as "lion" because Dutch gold coins stamped with lions circulated widely in the region in the 17c. and the word for "lion" came to be a word for "money" in some languages in the region.
leukaemia (n.)
alternative spelling of leukemia.
leukemia (n.)
1851, on model of German Leukämie (1848), coined by R. Virchow from Greek leukos "clear, white" (cognate with Gothic liuhaþ, Old English leoht "light;" see light (n.)) + haima "blood" (see -emia).
leukemic (adj.)
also leukaemic, 1852; see leukemia + -ic.
leukocyte (n.)
also leucocyte, 1860, via French leucocyte, from Greek leuko-, comb. form of leukos "white" (see light (n.)) + -cyte (see cyto-).
lev (n.)
monetary unit of Bulgaria, introduced 1881, literally "lion" (see leu).
Levant
"Mediterranean lands east of Italy," late 15c., from Middle French levant "the Orient," from present participle of lever "to rise" (from Latin levare "to raise;" see lever). The region so called in reference to the direction of sunrise.
Levantine (adj.)
1640s, from Levant + -ine (1).
levari facias
Latin, literally "cause to be levied."
levator (n.)
from medical Latin levator "a lifter," from Latin levatus, past participle of levare "to raise" (see lever).
levee (n.1)
1719, "natural or artificial embankment to prevent overflow of a river," from New Orleans French levée "raising, lifting; embankment," from French, originally fem. past participle of lever "to raise," from Latin levare "to raise" (see lever).
levee (n.2)
"morning assembly held by a prince or king (upon rising from bed)," 1670s, from French lever "a raising," noun use of verb meaning "to raise" (see levee (n.1)).
level (n.)
mid-14c., "tool to indicate a horizontal line," from Old French livel "a level" (13c.), ultimately from Latin libella "a balance, level," diminutive of libra "balance, scale, unit of weight," from PIE *lithra. Cognate Spanish nivel, Modern French niveau are from the same source but altered by dissimilation. Meaning "horizontality" is from c.1400. Meaning "position as marked by a horizontal line" is from 1530s. Phrase on the level "fair, honest" is from 1872; earlier it meant "moderate, without great ambition" (1790).
level (v.)
mid-15c., "to make level," from level (n.). From c.1600 as "to bring to a level;" 1958 as "to cease increasing." Meaning "to aim a gun" is late 15c. Slang sense of "tell the truth" is from 1920. To level up "to rise" is attested by 1863.
A word here as to the misconception labored under by our English neighbor; he evidently does not understand the American manner of doing things. We never level down in this country; we are always at work on the up grade. "Level up! Level up!" is the motto of the American people. [James E. Garretson, "Professional Education," in "The Dental Cosmos," Philadelphia, 1865]
To level off "cease rising or falling" is from 1920, originally in aviation.
level (adj.)
early 15c., from level (n.). To do one's level best is from 1851.
levelheaded (adj.)
also level-headed, 1869, from level (adj.) + head (n.). The notion is of "balanced." Related: Levelheadedness.
leveller (n.)
1590s, someone or something that makes level; agent noun of level (v.). From 1640s as the name of a political party of the time of Charles I that advocated abolishing all differences of position and rank.
lever (n.)
c.1300, from Old French levier (Modern French leveur) "a lifter, a lever," agent noun from lever "to raise," from Latin levare "to raise," from levis "light" in weight, from PIE root *legwh- "light, having little weight; easy, agile, nimble" (cognates: Sanskrit laghuh "quick, small;" Greek elakhys "small," elaphros "light;" Old Church Slavonic liguku, Lithuanian lengvas "light;" Old Irish laigiu "smaller, worse;" Gothic leihts, Old English leoht "light" (adj.)). As a verb, 1856, from the noun.
leverage (n.)
1724, "action of a lever," from lever (n.) + -age. Meaning "power or force of a lever" is from 1827; figurative sense from 1858. The financial sense is attested by 1933, American English; as a verb by 1956. Related: Leveraged; leverages; leveraging.
leveret (n.)
"young hare," early 15c., from Old French levrat, diminutive of levre (12c., Modern French lièvre) "hare," from Latin lepore, from lepus.
Levi
masc. proper name, biblical son of Jacob by Leah, from Hebrew lewi, literally "joining, pledging, attached," from stem of lawah "he joined."
leviathan (n.)
late 14c., "sea monster, sea serpent," also regarded as a form of Satan, from Late Latin leviathan, from Hebrew livyathan "dragon, serpent, huge sea animal," of unknown origin, perhaps related to liwyah "wreath," from root l-w-h- "to wind, turn, twist." Of powerful persons or things from c.1600. Hobbes's use is from 1651.
levirate (n.)
custom by which the male next-of-kin of a dead man was bound to marry his widow, 1725, from Latin levir "brother-in-law" (from PIE *daiwer- "husband's brother") + -ate (2).
Levis (n.)
1926, American English, originally Levi's, from Levi Strauss and Company, original manufacturer. Strauss' innovation was the copper rivets at strain points. A cowboy's accessory, adopted as a fashion c.1940s.
levitate (v.)
1670s, "to rise by virtue of lightness," from Latin levitas "lightness," patterned in English on gravitate. Sense of "raise (a person) into the air" is mainly from spiritualism (1870s). Related: Levitated; levitating.
levitation (n.)
1660s, noun of action from Latin levitas (see levitate) + -ion.
Leviticus
third book of the Pentateuch, c.1400, from Late Latin Leviticus (liber), literally "book of the Levites," from Greek to Leuitikon biblion, from Leuites, from Hebrew Lewi. Properly the part of the Pentateuch dealing with the function of the priests who were of the tribe of Levi (a portion of the tribe acted as assistants to the priests in the temple-worship). The Hebrew title is Torath Kohanim, literally "the law of the priests." Related: Levite; Levitical.
Levittown
used figuratively for "generic suburban tract housing," American English, from the vast planned real estate developments built by the firm Levitt & Sons Inc., the first on Long Island, 1946-51 (more than 17,000 homes), the second north of Philadelphia (1951-55).
levity (n.)
"want of seriousness, frivolity," 1560s, from Latin levitatem (nominative levitas) "lightness, frivolity," from levis "light" in weight (see lever) + -ity.
levo-
word-forming element meaning "toward the left," from French lévo-, from Latin laevus "left" (see left (adj.)).
levy (v.)
early 13c., "act of raising or collecting," from Anglo-French leve, from Old French levée "act of raising," noun use of fem. past participle of lever "to raise" (see lever). Originally of taxes, later of men for armies (c.1500). Related: Levied; levying.
levy (n.)
"an act of levying," early 15c., from Anglo-French leve, Old French levée "a raising, lifting; levying," noun use of fem. past participle of lever "to raise" (see lever).
lewd (adj.)
Old English læwede "nonclerical," of uncertain origin but probably ultimately from Vulgar Latin *laigo-, from Latin laicus (see lay (adj.)). Sense of "unlettered, uneducated" (early 13c.) descended to "coarse, vile, lustful" by late 14c. Related: Lewdly; lewdness.
Lewis
masc. proper name, Anglo-French form of French Louis (see Louis).
lex talionis
1590s, Latin, "law of retaliation," from talionis, genitive of talio (see retaliation); an eye for an eye, a tooth for a tooth.
lexeme (n.)
1937, from lexicon + -eme, ending abstracted from morpheme. Related: Lexemic.
lexical (adj.)
1833, from Greek lexikos "pertaining to words" (see lexicon) + -al (1). Related: Lexically.
lexico-
word-forming element, from Latinized comb. form of Greek lexikos (see lexicon).
lexicographer (n.)
1650s, from French lexicographe "lexicographer," from Greek lexikographos, from lexikon "wordbook" (see lexicon) + -graphos "writer," from graphein "to write" (see -graphy).
lexicography (n.)
1670s, from lexico- + -graphy. Related: Lexicographic; lexicographical.
lexicology (n.)
1828, from lexico- + -logy.
lexicon (n.)
c.1600, "a dictionary," from Middle French lexicon or directly from Modern Latin lexicon, from Greek lexikon (biblion) "word (book)," from neuter of lexikos "pertaining to words," from lexis "word," from legein "say" (see lecture (n.)).

Used originally of dictionaries of Greek, Syriac, Hebrew and Arabic, because these typically were in Latin and in Modern Latin lexicon, not dictionarius, was the preferred word. The modern sense of "vocabulary proper to some sphere of activity" (1640s) is a figurative extension.
ley (n.)
"line of a prehistoric track; alignment of natural and artificial features," 1922 [Alfred Watkins], apparently a variant of lea. Popular topic in Britain in 1920s and 30s and again in 1960s-70s.