Etymology
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inactive (adj.)

"not active or acting," 1640s, from in- (1) "not, opposite of" + active. Perhaps a back-formation from inactivity.

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torpor (n.)

"lethargy, listlessness," c. 1600, from Latin torpor "numbness, sluggishness," from torpere "be numb, be inactive, be dull" (from PIE root *ster- (1) "stiff").

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deactivate (v.)

also de-activate, "render inactive or less active," 1904, from de- "do the opposite of" + activate. Related: Deactivated; deactivating; deactivation.

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do-nothing (n.)

"an idler," 1570s, from the verbal phrase; see do (v.) + nothing. As an adjective, "doing no work, indolent, inactive," by 1832.

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quiescence (n.)

"state or quality of being inactive," 1630s, from Latin quiescentia, from quiescere "to rest" (from suffixed form of PIE root *kweie- "to rest, be quiet"). Related: Quiescency.

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velleity (n.)
"volition in the weakest form; an indolent or inactive wish," 1610s, from Medieval Latin stem of velleitas (from Latin velle "to wish, will;" see will (v.)) + -ity.
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inert (adj.)
1640s, "without inherent force, having no power to act or respond," from French inerte (16c.) or directly from Latin inertem (nominative iners) "unskilled, incompetent; inactive, helpless, weak, sluggish; worthless," used of stagnant fluids, uncultivated pastures, expressionless eyes. It is a compound of in- "without, not, opposite of" (see in- (1)) + ars (genitive artis) "skill" (see art (n.)). In chemistry, "having no active properties, neutral" (1800), specifically from 1885 of certain chemically inactive, colorless, odorless gases. Of persons or creatures, "indisposed or unable to move or act," from 1774.
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nurse (n.2)

"dogfish, shark," a name given to various sharks of inactive habits, c. 1500, of unknown origin. Perhaps identical to nurse (n.1), but the sense is obscure, or perhaps a different word conformed to it by folk-etymology.

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lethargic (adj.)
late 14c., litargik, "morbidly drowsy, manifesting lethargy," from Latin lethargicus "affected with lethargy," from Greek lethargikos "drowsy," from lethargos "forgetful; inactive" (see lethargy). From 1590s as "pertaining to lethargy." Related: Lethargically. In 17c. also with a verb form, lethargize, and a noun, letharge "lethargic patient."
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drowsy (adj.)

"inclined to sleep, sleepy," 1520s, probably ultimately from Old English drusan, drusian "sink," also "become languid, slow, or inactive" (related to dreosan "to fall;" see dreary). There is no record of it in Middle English. Related: Drowsily; drowsiness.

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