1848, "to throw overboard," especially to save a ship in danger, from jettison (n.) "act of throwing overboard" to lighten a ship. This noun was an 18c. Marine Insurance writers' restoration of the earlier form and original sense of the 15c. word that had become jetsam, probably because jetsam had taken on a sense of "things cast overboard" and an unambiguous word was needed for "act of casting things overboard."
Middle English jetteson (n.) "act of throwing overboard" is from Anglo-French getteson, Old French getaison "act of throwing (goods overboard)," especially to lighten a ship in distress, from Late Latin iactationem (nominative iactatio) "a throwing, act of throwing," noun of action from past participle stem of iactare "to throw, toss about" (from PIE root *ye- "to throw, impel"). Related: Jettisoned.
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").
type of barge used in unloading, late 15c., agent noun from light (adj.1), with a sense of lightening a load, or else from or modeled on Dutch lichter, from lichten "to lighten, unload," on the same notion. They are used in loading or unloading ships that cannot approach a wharf. Related: Lighterman.
1560s, jottsome "act of throwing goods overboard to lighten a ship," alteration and contraction of Middle English jetteson, from Anglo-French getteson, Old French getaison "a throwing" (see jettison). Intermediate forms were jetson, jetsome; the form perhaps was deformed by influence of flotsam. From 1590s as "goods thrown overboard;" figurative use by 1861. For distinction of meaning, see flotsam.
"to descend (from horseback, etc.), dismount," Middle English alighten, from Old English alihtan "alight," originally "to lighten, take off, take away," from a- "down, aside" (see a- (1)) + lihtan "get off, make light" (see light (v.)). The notion is of getting down off a horse or vehicle, thus lightening it. Of aircraft (originally balloons) from 1786. Related: Alighted; alighting.
in sculpture, architecture, etc., "projection of figure or design from the flat surface on which it is formed," c. 1600, from French relief, from Italian rilievo, from rilevare "to raise," from Latin relevare "to raise, lighten" (see relieve). In physical geography, "the form of the surface of any part of the earth" (by 1842), especially in relief map.
Model Mapping.—The plan of representing countries in relief is gaining ground, particularly in Germany. [William Richard Hamilton, president's address to the Royal Geographical Society of London, May 23, 1842]
early 15c., "publish a 'thundering' denunciation; hurl condemnation (at an offender)," a figurative use, from Latin fulminatus, past participle of fulminare "hurl lightning, lighten," figuratively "to thunder," from fulmen (genitive fulminis) "lightning flash," related to fulgor "lightning," fulgere "to shine, flash," from PIE *bhleg- "to shine, flash," from root *bhel- (1) "to shine, flash, burn." Metaphoric sense (the oldest in English) in reference to formal condemnation is from Medieval Latin fulminare, used of formal ecclesiastical censures. Related: Fulminated; fulminating.
"put down, quiet, assuage, pacify," Middle English alegen, from Old English alecgan "to put, place, put down; remit, give up, suppress, abolish; diminish, lessen," from a- "down, aside" (see a- (1)) + lecgan "to lay" (see lay (v.)). A common Germanic compound (cognates: Gothic uslagjan "lay down," Old High German irleccan, German erlegen "to bring down").
Early Middle English pronunciations of -y- and -g- were not always distinct, and the word was confused in Middle English with various senses of Romanic-derived alloy (v.) and especially a now-obsolete verb allege "to alleviate, lighten" (from Latin alleviare, from ad "to" + levis "light" in weight; from PIE root *legwh- "not heavy, having little weight").
Amid the overlapping of meanings that thus arose, there was developed a perplexing network of uses of allay and allege, that belong entirely to no one of the original vbs., but combine the senses of two or more of them. [OED]
Hence the senses "lighten, alleviate; mix, temper, weaken." The confusion with the Latin words probably also accounts for the unetymological double -l-, attested from 17c. Related: Allayed; allaying.
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.
"a young swan," c. 1400, also signet before 17c., from Anglo-French cignet (mid-14c.), Anglo-Latin cygnettus, diminutives of Old French cigne, cisne "swan" (12c., Modern French cygne), from Latin cygnus, from Greek kyknos, which has been the subject of "abundant discussion" (Beekes) and is perhaps from PIE *(s)keuk- "to be white" (compare Sanskrit socati "to lighten, glow," sukra- "light, clear, white"). Spanish, Portuguese cisne, Italian cecero are from Medieval Latin cecinus, cicinus, a corruption of the classical Latin word.