Online Etymology Dictionary

LCD: 1973, initialism (acronym) from liquid crystal display, which is attested from 1968, from liquid crystal, a translation of German flüssiger krystall (1890).
le: French masc. definite article (including the old neuter), fem. la, from Latin ille "he, that," used in Late Latin and Medieval Latin as the definite article. Cognate with Spanish el.
lea (n.): Old English leah "open field, meadow, piece of untilled grassy ground," earlier læch, preserved in place names, from Proto-Germanic *laukhaz (source also of Old High German loh "clearing," and probably also Flemish -loo, which forms the second element in Waterloo), from PIE *louko- "light place" (source also of Sanskrit lokah "open space, free space, world," Latin lucus "grove, sacred grove, wood," Lithuanian laukas "open field, land"), perhaps from or related to *leuk- "to shine, be bright" (see light (n.)). The dative form is the source of many of the English surnames Lee, Leigh.
leach (v.): Old English leccan "to moisten, water, wet, irrigate" (see leak (v.)). The word disappears, then re-emerges late 18c. in a technological sense in reference to percolating liquids. Related: Leached; leaching. Hence leach (n.) "a separation of lye or alkali in solution."
leachate (n.): 1920, from leach + -ate (1).
lead (n.2): c. 1300, "action of leading," from lead (v.1). Meaning "the front or leading place" is from 1560s. Johnson stigmatized it as "a low, despicable word." Sense in card-playing, "action or privilege of playing first," is from 1742; in theater, "the principal part," from 1831; in journalism, "initial summary of a news story," from 1912 (often spelled lede to distinguish it from lead (n.1), which formerly played a prominent role in typesetting. Boxing sense is from 1906. In jazz bands, from 1934 in reference to the principal parts; earlier it was used in music in reference to fugues (1880) of the part that takes off first and is "followed" by the others.

Meaning "direction given by example" (as in follow (someone's) lead) is by 1863, that of "a clue to a solution" is by 1851, both from the notion of "thing to be followed." As an adjective, "leading," by 1846. Lead-time "time needed to produce something" is 1945, American English.
lead (v.2): early 15c., "to make of lead," from lead (n.1). Meaning "to cover with lead" is from mid-15c. In printing, 1841, also lead out.
lead (adj.): "made of or resembling lead," late 14c., from lead (n.1).
lead (n.1): heavy metal, Old English lead "lead, leaden vessel," from West Germanic *loudhom (source also of Old Frisian lad, Middle Dutch loot, Dutch lood "lead," German Lot "weight, plummet"), a word of uncertain origin. The name and the skill in using the metal seem to have been borrowed from the Celts (compare Old Irish luaide).

Figurative of heaviness since at least early 14c. Lead balloon "a failure," American English slang, attested by 1957 (as a type of something heavy that can be kept up only with effort, from 1904). Lead-footed "slow" is from 1896; opposite sense of "fast" emerged 1940s in trucker's jargon, from notion of a foot heavy on the gas pedal.

Meaning "graphite in a pencil" is from 1816 (see pencil (n.)). Black lead was an old name for "graphite," hence lead pencil (1680s) and the colloquial figurative phrase to have lead in one's pencil "be possessed of (especially male sexual) vigor," attested by 1902. White lead (1560s) was an old name for "tin."

As a name of a dull bluish-gray color, 1610s. From 1590s as figurative for "bullets." Lead oxide was much used in glazing, mirror-making, and pigments. In printing, "thin strip of type-metal (often lead but sometimes brass) used in composition to separate lines" from 1808, earlier space-line. Lead-poisoning is from 1848; earlier lead-distemper (1774).
lead (v.1): "to guide," Old English lædan (transitive) "cause to go with oneself; march at the head of, go before as a guide, accompany and show the way; carry on; sprout forth, bring forth; pass (one's life)," causative of liðan "to travel," from Proto-Germanic *laidjan (source also of Old Saxon lithan, Old Norse liða "to go," Old High German ga-lidan "to travel," Gothic ga-leiþan "to go"), from PIE *leit- (2) "to go forth."

Of roads, c. 1200. Meaning "to be in first place" is from late 14c. Intransitive sense, "act the part of a leader," is from 1570s. Sense in card playing, "to commence a round or trick," is from 1670s. Meaning "take the directing part in a musical performance or prayer" is from 1849. Related: Led; leading.

To lead with one's chin "leave oneself vulnerable in a contest" (1946) is a figure from boxing. To lead on "entice to advance" is from 1590s. To figuratively lead (someone) by the nose "guide by persuasion" is from 1580s, from draught animals (earlier lead by the sleeve, early 15c.). To lead (someone) a dance "compel through a course of irksome actions" is from 1520s.
lead-in (n.): 1913, in electrical wiring, from verbal phrase; see lead (v.1) + in (adv.). General sense of "introduction, opening" is from 1928, originally in music.
lead-off (n.): "commencement, beginning," 1879, from verbal phrase (attested from 1806); see lead (v.1) + off (adv.).
lead-up (n.): 1917, from verbal phrase; see lead (v.1) + up (adv.). To lead up to "prepare gradually for" is from 1861.
leaded (adj.): early 13c., "covered with lead," from lead (n.1). In reference to printed matter, "set with more than ordinary space between the lines," 1864. Of fuel, "with added lead," 1936.
leaden (adj.): "made of lead," Old English leaden, from lead (n.1) + -en (2). The figurative sense of "heavy, oppressive, dull" is attested by 1570s. Related: Leadenly; leadenness.
leader (n.): Old English lædere "one who leads, one first or most prominent," agent noun from lædan "to guide, conduct" (see lead (v.)). Cognate with Old Frisian ledera, Dutch leider, Old High German leitari, German Leiter. As a title for the head of an authoritarian state, from 1918 (translating Führer, Duce, caudillo, etc.). Meaning "writing or statement meant to begin a discussion or debate" is late 13c.; in modern use often short for leading article (1807) "opinion piece in a British newspaper" (leader in this sense attested from 1837). The golf course leader board so called from 1970.
leaderless (adj.): 1590s, from leader (n.1) + -less. Related: Leaderlessly; leaderlessness.
leadership (n.): 1821, "position of a leader, command," from leader + -ship. Sense extended by late 19c. to "characteristics necessary to be a leader, capacity to lead."
leading (n.2): mid-13c., "a bringing by force," verbal noun from lead (v.1). Meaning "direction, guidance" is from late 14c.
leading (n.1): "lead work; lead covering or frame of lead," mid-15c., verbal noun from lead (n.1). Printing sense is from 1855.
leading (adj.): 1590s, "that goes first," present participle adjective from lead (v.1). Meaning "directing, guiding" is from 1620s. Of persons, "having first or most prominent place," 1670s. In reference to theatrical companies, leading lady is from 1846; leading man from 1847.
leaf (v.): "to turn over (the pages of a book)," 1660s, from leaf (n.). Meaning "put forth leaves or foliage" is from 1610s. Related: Leafed; leaved; leafing.
leaf (n.): Old English leaf "leaf of a plant, foliage; page of a book, sheet of paper," from Proto-Germanic *laubaz (source also of Old Saxon lof, Old Norse lauf, Old Frisian laf, Dutch loof, Old High German loub, German Laub "foliage, leaves," Gothic laufs "leaf, foliage"), probably from PIE *leub(h)- "to peel off, strip or break off" ((source also of Old Irish luib, "herb," lub-gort "garden;" Albanian labë "rind, cork;" Lithuanian luba "plank, board;" Russian lob "forehead, brow," Czech leb "skull;" Lithuanian luobas "bast," Latvian luobas "peel," Russian lub "bast;" Old Norse lyf "medicinal herbs," Old English lybb "poison; magic").

Related to lodge and lobby; for another PIE root see folio. Extended late 14c. to very thin sheets of metal (especially gold). Compare Lithuanian lapas "leaf," from a root also in Greek lepos "bark," lepein "to peel off." Also applied to flat and relatively broad surfaces, especially of flexible or mounted attachments; meaning "hinged flap on the side of a table" is from 1550s. To turn over a (new) leaf (1590s; 1570s as turn the leaf) "begin a new and better course of life" is a reference to the book sense. Among insects, leaf-hopper is from 1847; leaf-cutter from 1816.
leafless (adj.): 1580s, from leaf (n.) + -less.
leaflet (n.): 1787 as a term in botany; 1867 as a term in printing and publication; diminutive of leaf (n.) with -let.
A newspaperman asked the British authorities for a copy of the leaflets distributed in Germany by British airplanes. According to the London Daily Herald, his request was refused with the following answer: "Copies are not given out, as they might fall into enemy hands." ["The Living Age" magazine, Sept. 1939-Feb. 1940]
leafy (adj.): 1550s, from leaf (n.) + -y (2). Related: Leafily; leafiness.
league (n.1): "alliance," mid-15c., ligg, from Middle French ligue "confederacy, league" (15c.), from Italian lega, from legare "to tie, to bind," from Latin ligare "to bind" (see ligament). Originally among nations, subsequently extended to political associations (1846) and sports associations (1879). League of Nations first attested 1917 (created 1919).
league (v.): "to form a league," 1610s, from league (n.1). Related: Leagued; leaguing.
league (n.2): itinerary unit in medieval England, distance of about three statute miles, late 14c., ultimately from Late Latin leuga (source also of French lieue, Spanish legua, Italian lega), which is said by Roman writers to be from Gaulish. A vague measure (perhaps originally an hour's hike), in England it was a conventional, not a legal measure, and in English it is found more often in poetic than in practical writing.
leak (v.): "to let water in or out" [Johnson], late 14c., from Middle Dutch leken "to drip, to leak," or from Old Norse leka, both of them related to Old English leccan "to moisten, water, irrigate" (which did not survive into Middle English), all from Proto-Germanic *lek- "deficiency" (source also of Old High German lecchen "to become dry," German lechzen "to be parched with thirst"), from PIE root *leg- (2) "to dribble, trickle." The figurative meaning "come to be known in spite of efforts at concealment" dates from at least 1832; transitive sense first recorded 1859. Related: Leaked; leaking.
leak (n.): "hole by which liquid enters or escapes," late 15c., from leak (v.) or Old Norse cognate leka. Sense of "revelation of secret information" is from 1950. Meaning "act of urination" is attested from 1934 ("Tropic of Cancer"); but the verb meaning "to piss" is from 1590s: "Why, you will allow vs ne're a Iourden [i.e. a chamberpot], and then we leake in your Chimney." ["I Hen. IV," II.i.22]
leakage (n.): late 15c., from leak (v.) + -age.
leaky (adj.): mid-15c., from leak (n.) + -y (2). Related: Leakiness. Slang sense of "unable to keep a secret" attested from 1704.
leal (adj.): "loyal, faithful, honest, true," c. 1300, lele, surviving from Middle English as Northern English and Scottish form of loyal. But the Land of the leal (Lady Nairne) is Heaven, not Scotland. Related: Lealty.
lean (adj.): "thin, spare, with little flesh or fat," c. 1200, from Old English hlæne "lean, thin," possibly (Skeat) from hlænan "cause to lean or bend," from Proto-Germanic *khlainijan, which would connect it to Old English hleonian (see lean (v.)). But perhaps rather, according to OED, from a PIE *qloinio- (with cognates in Lithuanian klynas "scrap, fragment," Lettish kleins "feeble"). Extended and figurative senses from early 14c.
lean (n.2): c. 1200, "lean animals or persons," from lean (adj.). Meaning "lean part of anything, muscle without fat, lean meat" is mid-15c.
lean (n.1): "action or state of leaning, deviation from a vertical position," 1776, from lean (v.).
lean (v.): c. 1200, from Old English hlinian "to recline, lie down, rest; band or incline" (Mercian hleonian, Northumbrian hlionian), from Proto-Germanic *khlinen (source also of Old Saxon hlinon, Old Frisian lena, Middle Dutch lenen, Dutch leunen, Old High German hlinen, German lehnen "to lean"), from PIE root *klei- "to lean, to incline" (source also of Sanskrit srayati "leans," sritah "leaning;" Old Persian cay "to lean;" Lithuanian slyti "to slope," slieti "to lean;" Latin clinare "to lean, bend," clivus "declivity," inclinare "cause to bend," declinare "bend down, turn aside;" Greek klinein "to cause to slope, slant, incline;" Old Irish cloin "crooked, wrong;" Middle Irish cle, Welsh cledd "left," literally "slanting").

Transitive sense "cause to lean or rest" is from 14c. Meaning "to incline the body against something for support" is mid-13c. Figurative sense of "to trust for support" is from early 13c. Sense of "to lean toward mentally, to favor" is from late 14c. Related: Leaned; leaning. Colloquial lean on "put pressure on" (someone) is first recorded 1960.
lean-to (n.): "building whose rafters lean against another building or wall," mid-15c., from lean (v.) + to (adv.). Compare penthouse. "An addition made to a house behind, or at the end of it, chiefly for domestic offices, of one story or more, lower than the main building, and the roof of it leaning against the wall of the house" [Bartlett].
Leander: youth of Abydos, lover of Hero. He swam nightly across the Hellespont to visit her in Sestos, on the Thracian side, until he drowned. The name is from Greek Leiandros, literally "lion-man," from leon "lion" + aner (genitive andros) "man" (see anthropo-).
leaning (n.): Old English hlininga; verbal noun from lean (v.). Figurative sense "inclination, tendency" is from 1580s. Related: Leanings.
leanness (n.): Old English hlænnesse; see lean (adj.) + -ness.
leant: occasion past tense and past participle of lean (v.).
leap (v.): c. 1200, from Old English hleapan "to jump, spring clear of the ground by force of an initial bound; run, go; dance, leap upon (a horse)" (class VII strong verb; past tense hleop, past participle hleapen), from Proto-Germanic *hlaupan (source also of Old Saxon hlopan, Old Norse hlaupa, Old Frisian hlapa, Dutch lopen, Old High German hlouffan, German laufen "to run," Gothic us-hlaupan "to jump up"), of uncertain origin, with no known cognates beyond Germanic.
First loke and aftirward lepe [proverb recorded from mid-15c.]
Transitive sense "pass over by leaping" is from early 15c. Leap-frog, the children's game, is attested by that name from 1590s ("Henry V"); figurative use by 1704; as a verb from 1872. Related: Leaped; leaping.
leap (n.): c. 1200, "the act or an act of leaping," from Old English hliep, hlyp (West Saxon), *hlep (Mercian, Northumbrian) "a leap, a bound, a spring; sudden movement; thing to leap from;" from Proto-Germanic *hlaupan (cognates: Old Frisian hlep, Dutch loop, Old High German hlouf, German lauf); from the root of leap (v.). Leaps has been paired with bounds since at least 1720.
leap year (n.): "year containing 366 days," late 14c., lepe gere (not in Old English), from leap (v.) + year. Probably so called from its causing fixed festival days, which normally advance one weekday per year, to "leap" ahead one day in the week. Compare Medieval Latin saltus lunae (Old English monan hlyp) "omission of one day in the lunar calendar every 19 years."

Dutch schrikkeljaar "leap year" is from Middle Dutch schricken "leap forward," literally "be startled, be in fear." The 29th of February is schrikkeldag. Danish skudaar, Swedish skottår are literally "shoot-year;" German schaltjahr is from schalten "insert, intercalate." The Late Latin phrase was annus bissextilis, source of the Romanic words; compare bissextile.
learn (v.): Old English leornian "to get knowledge, be cultivated; study, read, think about," from Proto-Germanic *liznojan (cognates: Old Frisian lernia, Middle Dutch leeren, Dutch leren, Old High German lernen, German lernen "to learn," Gothic lais "I know"), with a base sense of "to follow or find the track," from PIE *leis- (1) "track, furrow." Related to German Gleis "track," and to Old English læst "sole of the foot" (see last (n.1)).

From c. 1200 as "to hear of, ascertain." Transitive use (He learned me (how) to read), now considered vulgar (except in reflexive expressions, I learn English), was acceptable from c. 1200 until early 19c. It is preserved in past participle adjective learned "having knowledge gained by study." Old English also had læran "to teach" (see lere). Related: Learning.
learnable (adj.): 1620s, from learn + -able. Related: Learnability.
learned (adj.): "having knowledge gained by study," mid-14c., past participle adjective from learn (v.) in its former transitive sense. Related: Learnedly; learnedness. "[L]earned expresses depth and fullness in the knowledge, while scholarly expresses accuracy" [Century Dictionary].
learning (n.): Old English leornung "study, action of acquiring knowledge," verbal noun from leornian (see learn). Meaning "knowledge acquired by systematic study, extensive literary and scientific culture" is from mid-14c. Learning curve attested by 1907.