Etymology
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alleviation (n.)

early 15c., "mitigation, relief," from Medieval Latin alleviationem (nominative alleviatio), noun of action from past-participle stem of alleviare "lift up, raise," figuratively "to lighten (a burden), comfort, console," from assimilated form of Latin ad "to" (see ad-) + levis "light" in weight (from PIE root *legwh- "not heavy, having little weight").

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levity (n.)
1560s, "want of seriousness, frivolity," from French levite, from Latin levitatem (nominative levitas) "lightness," literal and figurative; "light-mindedness, frivolity," from levis "light" in weight, from PIE root *legwh- "not heavy, having little weight." In old science (16c.-17c.), the name of a force or property of physical bodies, the opposite of gravity, causing them to tend to rise.
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alleviate (v.)
early 15c., " to mitigate, relieve (sorrows, suffering, etc.)," from Late Latin alleviatus, past participle of alleviare "lift up, raise," figuratively "to lighten (a burden), comfort, console," from assimilated form of Latin ad "to" (see ad-) + levis "light" in weight (from PIE root *legwh- "not heavy, having little weight"). Related: Alleviated; alleviating.
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elevation (n.)

late 14c., "a rising, height of something, height to which something is elevated," from Old French elevation and directly from Latin elevationem (nominative elevatio) "a lifting up," noun of action from past-participle stem of elevare "lift up, raise," figuratively, "to lighten, alleviate," from ex "out" (see ex-) + levare "to lighten; to raise," from levis "light" in weight (from PIE root *legwh- "not heavy, having little weight"). Meaning "act of elevating" is from 1520s.

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elevate (v.)
late 15c., "to raise above the usual position," from Latin elevatus, past participle of elevare "lift up, raise," figuratively, "to lighten, alleviate," from ex "out" (see ex-) + levare "lighten, raise," from levis "light" in weight (from PIE root *legwh- "not heavy, having little weight"). Sense of "raise in rank or status" is from c. 1500. Moral or intellectual sense is from 1620s. Related: Elevated (which also was old slang for "drunk"); elevating.
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legerdemain (n.)

early 15c., "conjuring tricks, sleight of hand," from Old French léger de main "quick of hand," literally "light of hand." Léger "light" in weight (Old French legier, 12c.) is from Latin levis "light" (from PIE root *legwh- "not heavy, having little weight"). It is cognate with Spanish ligero, Italian leggiero "light, nimble" (hence also leger line or ledger line in music). Main "hand" is from Latin manus (from PIE root *man- (2) "hand").

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lever (n.)
"simple machine consisting of a rigid piece acted upon at different points by two forces," c. 1300, from Old French levier (12c.) "a lifter, a lever, crowbar," agent noun from lever "to raise" (10c.), from Latin levare "to raise," from levis "light" in weight, "not heavy," also, of motion, "quick, rapid, nimble;" of food, "easy to digest;" figuratively "slight, trifling, unimportant; fickle, inconsistent;" of punishments, etc., "not severe," from PIE root *legwh- "not heavy, having little weight." As a verb, 1856, from the noun.
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oblivion (n.)

late 14c., oblivioun, "state or fact of forgetting, forgetfulness, loss of memory," from Old French oblivion (13c.) and directly from Latin oblivionem (nominative oblivio) "forgetfulness; a being forgotten," from oblivisci (past participle oblitus) "forget," which is of uncertain origin.

Perhaps originally "even out, smooth over, efface," from ob "over" (see ob-) + root of lēvis "smooth," but de Vaan and others find that "a semantic shift from 'to be smooth' to 'to forget' is not very convincing." However no better explanation has emerged. Latin lēvis also meant "rubbed smooth, ground down," from PIE *lehiu-, from root *(s)lei- "slime, slimy, sticky" (see slime (n.)); for sense evolution, compare obliterate.

Meaning "state or condition of being forgotten or lost to memory" is from early 15c. In English history, the Acts of Oblivion use the word in the sense of "intentional overlooking" (1610s), especially of political offenses. Related: Obliviously; obliviousness.

Oblivion is the state into which a thing passes when it is thoroughly and finally forgotten. ... Forgetfulness is a quality of a person: as a man remarkable for his forgetfulness. ... Obliviousness stands for a sort of negative act, a complete failure to remember: as a person's obliviousness of the proprieties of an occasion. [Century Dictionary]
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relieve (v.)

late 14c., releven, "alleviate (pain, etc.) wholly or partly, mitigate; afford comfort; allow respite; diminish the pressure of," also "give alms to, provide for;" also figuratively, "take heart, cheer up;" from Old French relever "to raise, relieve" (11c.) and directly from Latin relevare "to raise, alleviate, lift up, free from a burden," from re-, here perhaps an intensive prefix (see re-), + levare "to lift up, lighten," from levis "not heavy" (from PIE root *legwh- "not heavy, having little weight").

The notion is "to raise (someone) out of trouble." From c. 1400 as "advance to the rescue in battle, bring help to a besieged place;" also "return from battle; recall (troops)." Meaning "release from duty" is from early 15c. Related: relieved; relieving.

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lung (n.)

human or animal respiratory organ, c. 1300, from Old English lungen (plural), from Proto-Germanic *lunganjo- (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.

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