Etymology
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knockoff (n.)
also knock-off, "cheap imitation," 1966, from the verbal phrase knock off "do hastily" (1817), in reference to the casual way the things are made. The verbal phrase knock off is attested from 1640s as "desist, stop" (work, study, etc.), hence knockoff (n.) "act of leaving work" (1899) and, probably, the command knock it off "stop it" (1880), which was perhaps reinforced by the auctioneer's use of the term for "dispose of quickly." To knock (someone) off in the underworld slang sense of "kill, murder" is from 1919. See knock (v.) + off (adv.).
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derail (v.)

1850 (Dionysius Lardner, "Railway Economy"), in both transitive and intransitive senses, "cause to leave the rails or run off the tracks; to run off the rails or tracks," from French dérailler "to go off the rails," from de- (see de-) + railler (see rail (n.1)). Related: Derailed; derailing.

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Obie 
one of the annual awards given to off-Broadway theater, 1967, from O.B. as the abbreviation of Off-Broadway.
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standoffish (adj.)
1826, from verbal phrase stand off "hold aloof" (c. 1600); see stand (v.) + off (adv.). Related: Standoffishly; standoffishness.
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amputation (n.)

1610s, "a cutting off of tree branches, a pruning," also "operation of cutting off a limb, etc., of a body," from French amputation or directly from Latin amputationem (nominative amputatio), noun of action from past-participle stem of amputare "to cut off, lop off; cut around, to prune," from am(bi)- "around" (from PIE root *ambhi- "around") + putare "to prune, trim" (from PIE root *pau- (2) "to cut, strike, stamp").

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abscissa (n.)
Origin and meaning of abscissa
1798 in Latin form, earlier Englished as abscisse (1690s), from Latin abscissa, short for abscissa (linea) "(a line) cut off," or (recta ex diametro) abscissa "(a line) cut off (from the diameter)," fem. of abscissus "cut off," past participle of abscindere "to cut off, divide, part, separate," from ab "off, away from" (see ab-) + scindere "to cut, rend, tear asunder, split; split up, part, divide, separate," from PIE *skind-, from root *skei- "to cut, split." The Latin word translates Greek apolambanomene.
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exhaustion (n.)

1640s, "fatigue," noun of action from exhaust (v.) in sense of "drawing off" of strength. The etymological sense "act of drawing out or draining off" is by 1660s in English.

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alight (v.)
"to descend (from horseback, etc.), dismount," 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.
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exuviae (n.)
"cast-off skins, shells, or other coverings of animals," 1650s, Latin, literally "that which is stripped off," hence "slough, skin," also "clothing, equipment, arms, booty, spoils," from stem of exuere "to doff," from ex "off" (see ex-) + from PIE root *eu- "to dress" (also found in Latin induere "to dress," reduvia "fragment").
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abrade (v.)
Origin and meaning of abrade

""to rub or wear away; rub or scrape off," 1670s, from Latin abradere "to scrape off, shave away," from ab "off" (see ab-) + radere "to scrape" (see raze (v.)). Abrase, from the stem of the Latin verb, is attested from 1590s. Related: Abraded; abrading.

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