luminescence (n.) Look up luminescence at Dictionary.com
1884, from Latin lumen (genitive luminis) "light" (see luminous) + -escence.
Fluorescence and Phosphorescence -- Prof. E. Wiedmann has made a new study of these phenomena. He proposes the general name luminescence for evolutions of light which do not depend on the temperature of the substance concerned. ["Photographic News," April 20, 1888]
luminescent Look up luminescent at Dictionary.com
1889, from luminescence + -ent.
luminosity (n.) Look up luminosity at Dictionary.com
1630s, "quality of being luminous," from French luminosité or else a native formation from luminous + -ity. In astronomy, "intrinsic brightness of a heavenly body" (as distinguished from apparent magnitude, which diminishes with distance), attested from 1906.
luminous (adj.) Look up luminous at Dictionary.com
early 15c., "full of light," from Latin luminosus "shining, full of light," from lumen (genitive luminis) "light," related to lucere "to shine" (see light (n.)). Related: Luminously.
lummox (n.) Look up lummox at Dictionary.com
1825, East Anglian slang, perhaps from dumb ox, influenced by lumbering; or from E. Anglian dialectal form of verb lummock "move heavily or clumsily," of uncertain origin.
lump (n.) Look up lump at Dictionary.com
early 14c., lumpe (1224 as surname), probably in Old English, perhaps from a Scandinavian source (compare Danish lumpe, 16c.), of unknown origin. Compare also Middle High German lumpe, early modern Dutch lompe. Phrase lump in (one's) throat "feeling of tightness brought on by emotion" is from 1803. Lumps "hard knocks, a beating" is colloquial, from 1934. Lump sum, one covering a number of items, is from 1867.
lump (v.2) Look up lump at Dictionary.com
"endure" (now usually in contrast to like), 1791, apparently an extended sense from an older meaning "to look sulky, dislike" (1570s), of unknown origin, perhaps a symbolic sound (compare grump, harumph, etc.). Related: Lumped; lumping.
LUMPING. Great. A lumping pennyworth; a great qualtity for the money, a bargain. He has got a lumping pennyworth; frequently said of a man who marries a fat woman. [Grose, "Classical Dictionary of the Vulgar Tongue," 3rd edition, 1796]
lump (v.1) Look up lump at Dictionary.com
early 15c., "to curl up in a ball, to gather into a lump" (implied in lumped), from lump (n.). Meaning "to put together in one mass or group" is from 1620s. Related: Lumped; lumping.
lumpectomy (n.) Look up lumpectomy at Dictionary.com
1971, from lump (n.), coined on model of mastectomy.
lumpenproletariat (n.) Look up lumpenproletariat at Dictionary.com
1897, from German Lumpenproletariat (1850), from Karl Marx, who coined it to mean "rabble, poorest of the working class," from German lump "ragamuffin" + proletariat. Secondary sense of "boorish, stupid people" led to lumpen- being taken as a suffix meaning "unenlightened."
lumpy (adj.) Look up lumpy at Dictionary.com
1707, from lump (n.) + -y (2). Related: Lumpiness.
Luna (n.) Look up Luna at Dictionary.com
late 14c. "moon," also an alchemical name for "silver;" from Latin luna "moon, goddess of the moon," from *leuksna- (source also of Old Church Slavonic luna "moon," Old Prussian lauxnos "stars," Middle Irish luan "light, moon"), from the same source as lux, lumen "light," lucere "to shine" (see light (n.)). The luna moth (1841, American English) so called for the crescent-shaped markings on its wings. Lunarian (1708) was an early word for "inhabitant of the moon."
lunacy (n.) Look up lunacy at Dictionary.com
1540s, "condition of being a lunatic," formed in English from lunatic + -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."
lunar (adj.) Look up lunar at Dictionary.com
"crescent-shaped," early 15c.; "pertaining to the moon," 1620s, from Old French lunaire (15c.), from Latin lunaris "of the moon," from luna "moon" (with capital L- "moon goddess"); see Luna.
lunate (adj.) Look up lunate at Dictionary.com
"crescent-shaped," 1777, from Latin lunatus, from luna (see Luna).
lunatic (adj.) Look up lunatic at Dictionary.com
late 13c., "affected with periodic insanity, dependent on the changes of the moon," from Old French lunatique, lunage "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."
lunatic (n.) Look up lunatic at Dictionary.com
"lunatic person," late 14c., from lunatic (adj.).
lunation (n.) Look up lunation at Dictionary.com
"time from one new moon to another," late 14c., from Medieval Latin lunationem, from luna "moon" (see Luna).
lunch (n.) Look up lunch at Dictionary.com
"mid-day repast," 1786, shortened form of luncheon (q.v.). 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]
But as late as 1817 the only definition of lunch in Webster's is "a large piece of food." 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 (n.) is from 1821; lunch hour is from 1840. Slang phrase out to lunch "insane, stupid, clueless" first recorded 1955, on notion of being "not there." Old English had nonmete "afternoon meal," literally "noon-meat."
luncheon (n.) Look up luncheon at Dictionary.com
"light repast between mealtimes," 1650s (lunching; spelling luncheon by 1706); earlier "thick piece, hunk," 1570s (luncheon), of uncertain origin. Perhaps northern English dialectal lunch "hunk of bread or cheese" (1580s; 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 much later. It suggests perhaps an analogy with truncheon, etc. Especially in reference to an early afternoon meal eaten by those who have a noontime dinner.
luncheonette (n.) Look up luncheonette at Dictionary.com
type of restaurant, 1906, American English, from luncheon + diminutive ending -ette.
lune (n.) Look up lune at Dictionary.com
figure formed by two arcs of circles, 1704, from Latin luna "moon; crescent-shaped badge" (see luna).
lunette (n.) Look up lunette at Dictionary.com
1570s, "semi-circular 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 a crescent moon.
lung (n.) Look up lung at Dictionary.com
"human 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 *legwh- "not heavy, having little weight; easy, agile, nimble" (source also of Russian lëgkij, Polish lekki "light;" Russian lëgkoje "lung," Greek elaphros "light" in weight; see also lever).

The notion probably is from the fact that, when thrown into a pot of water, lungs of a slaughtered animal float, while the heart, liver, etc., do not. Compare also 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 attested from 1882.
lunge (n.) Look up lunge at Dictionary.com
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.)).
lunge (v.) Look up lunge at Dictionary.com
1735 (implied in lunged), from lunge (n.). Sense of "to make a sudden forward rush" is from 1821. Related: Lunged; lunging.
lungfish (n.) Look up lungfish at Dictionary.com
1883, from lung + fish (n.).
lunk (n.) Look up lunk at Dictionary.com
"slow-witted person," 1867, American English colloquial, shortened from lunkhead (1852), possibly an altered form of lump (n.) + head (n.)
Lupercalia (n.) Look up Lupercalia at Dictionary.com
Roman festival held Feb. 15, in honor of Lupercus, god (identified with Lycean Pan) 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.)).
lupin (n.) Look up lupin at Dictionary.com
plant of the genus lupinus, late 14c., from Latin lupinus, name of the plant, noun use of an adjective meaning "of a wolf" (see lupine). The reason for association with the animal is unclear; perhaps it was so called because of a belief that the plants were harmful to soil (compare lupus).
lupine (adj.) Look up lupine at Dictionary.com
"wolf-like," 1650s, from French lupine "wolf-like," from Latin lupinus "of the wolf," from lupus "wolf" (see wolf (n.)).
lupus (n.) Look up lupus at Dictionary.com
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.
lurch (n.1) Look up lurch at Dictionary.com
"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]; 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) Look up lurch at Dictionary.com
"predicament," 1580s, from Middle English lurch (v.) "to beat in a game of skill (often by a great many points)," mid-14c., probably literally "to make a complete victory in lorche," a game akin to backgammon, from Old French lourche. The game name is perhaps related to Middle English lurken, lorken "to lie hidden, lie in ambush," or it may be adopted into French from Middle High German lurz "left," also "wrong."
lurch (v.) Look up lurch at Dictionary.com
1821, from lurch (n.1). Related: Lurched; lurching.
lure (n.) Look up lure at Dictionary.com
early 14c., "something which allures or entices, an attraction" (a figurative use), also "bait for recalling hawks," from Anglo-French lure, Old French loirre "device used to recall hawks, lure," from Frankish *loþr 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).

Originally a bunch of feathers on a long cord, from which the hawk is fed during its training. Used of means of alluring other animals (especially fish) from c. 1700. Technically, bait is something the animal can eat; lure is a more general term. Also in 15c. a collective word for a group of young women.
lure (v.) Look up lure at Dictionary.com
late 14c., of hawks, also of persons, from lure (n.). Related: Lured; luring.
lurid (adj.) Look up lurid at Dictionary.com
1650s, "pale," from Latin luridus "pale yellow, ghastly," of uncertain origin, perhaps cognate with Greek khloros (see Chloe). Meaning "glowing in the darkness" is from 1727. The figurative sense of "sensational" is first attested 1850. Related: Luridly.
lurk (v.) Look up lurk at Dictionary.com
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)). Related: Lurked; lurking.
lurker (n.) Look up lurker at Dictionary.com
"one who lurks," early 14c., agent noun from lurk (v.).
luscious (adj.) Look up luscious at Dictionary.com
late 15c., perhaps a variant (with form perhaps influenced by Old French luxure, lusure) of Middle English licius "delicious" (c. 1400), which is perhaps a shortening of delicious, but OED is against this. Related: Lusciously; lusciousness.
lush (adj.) Look up lush at Dictionary.com
mid-15c., "lax, flaccid, soft, tender," from Old French lasche "soft, succulent," from laschier "loosen," from Late Latin laxicare "become shaky," related to Latin laxare "loosen," from laxus "loose" (see lax). Sense of "luxuriant in growth" is first attested c. 1600, in Shakespeare. Applied to colors since 1744. Related: Lushly; lushness.
lush (n.) Look up lush at Dictionary.com
"drunkard," 1890, from earlier (1790) slang meaning "liquor" (especially in phrase lush ken "alehouse"); perhaps a humorous use of lush (adj.) or from Romany or Shelta (tinkers' jargon).
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]
Lusitania Look up Lusitania at Dictionary.com
Latin name of a region roughly corresponding to modern Portugal; 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.
lusory (adj.) Look up lusory at Dictionary.com
1650s, from Latin lusorius "belonging to a player," from lusor "player," from stem of ludere "to play" (see ludicrous). Related: Lusorious.
lust (n.) Look up lust at Dictionary.com
Old English lust "desire, appetite, pleasure; sensuous appetite," from Proto-Germanic *lustuz (source also of Old Saxon, Old Frisian, Dutch, German lust, Old Norse lyst, Gothic lustus "pleasure, desire, lust"), 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). 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 [I John ii:16]); the cognate words in other Germanic languages tend still to mean simply "pleasure."
lust (v.) Look up lust at Dictionary.com
c. 1200, "to wish, to desire," from lust (n.) and Old English lystan (see list (v.4)). Sense of "to have a strong sexual desire (for or after)" is first attested 1520s in biblical use. Related: Lusted; lusting.
luster (n.1) Look up luster at Dictionary.com
"gloss, radiance," 1520s, from Middle French lustre "gloss, radiance" (14c.), common Romanic (cognates: Spanish and Portuguese lustre, Rumanian lustru, Italian lustro "splendor, brilliancy"), from Latin lustrare "spread light over, brighten, illumine," related to lucere "shine," lux "light" (see light (n.)).
luster (n.2) Look up luster at Dictionary.com
"one who lusts," 1590s, agent noun from lust (v.).
lustful (adj.) Look up lustful at Dictionary.com
Old English lustfull "wishful, desirous, having an eager desire;" see lust (n.) + -ful. Specifically of sexual desire from 1570s. Related: Lustfully; lustfulness. Middle English also had lustsome, which was used in a sense of "voluptuous, lustful" from c. 1400. Old English had lustbære "desirable, pleasant, cheerful, joyous."