Etymology
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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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inertness (n.)
"inactivity; fact of being inert," 1660s, from inert + -ness.
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inertia (n.)
1713, "that property of matter by virtue of which it retains its state of rest or of uniform rectilinear motion so long as no foreign cause changes that state" [Century Dictionary], introduced as a term in physics 17c. by German astronomer and physician Johann Kepler (1571-1630) as a special sense of Latin inertia "unskillfulness, ignorance; inactivity, idleness," from iners (genitive inertis) "unskilled; inactive" (see inert). Also sometimes vis inertia "force of inertia." Used in 1687 by Newton, writing in Modern Latin. The classical Latin sense of "apathy, passiveness, inactivity" is attested in English from 1822.
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*ar- 
also arə-, Proto-Indo-European root meaning "to fit together."

It forms all or part of: adorn; alarm; aristarchy; aristo-; aristocracy; arm (n.1) "upper limb of the body;" arm (n.2) "weapon;" armada; armadillo; armament; armature; armilla; armistice; armoire; armor; armory; army; art (n.) "skill as a result of learning or practice;" arthralgia; arthritis; arthro-; arthropod; arthroscopy; article; articulate; artifact; artifice; artisan; artist; coordination; disarm; gendarme; harmony; inert; inertia; inordinate; ordain; order; ordinal; ordinance; ordinary; ordinate; ordnance; ornament; ornate; primordial; subordinate; suborn.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit irmah "arm," rtih "manner, mode;" Armenian arnam "make," armukn "elbow;" Greek arti "just," artios "complete, suitable," artizein "to prepare," arthron "a joint;" Latin ars (stem art-) "art, skill, craft," armus "shoulder," artus "joint," arma "weapons;" Old Prussian irmo "arm;" German art "manner, mode."
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dead-weight (n.)

also deadweight, 1650s, "weight of an inert body," from dead (adj.) + weight (n.). Hence, "a heavy or oppressive burden" (1721).

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logged (adj.)
c. 1820, "reduced to the condition of a log" (n.1), which was old sailors' slang for an incapacitated wooden ship; thus "inert in the water."
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bovine (adj.)
1817, "of or like oxen," from French bovin (14c.), from Late Latin bovinus, from Latin bos (genitive bovis) "cow," originally "ox," "a loan word from a rural dialect" [Buck, who cites Umbrian bue], from PIE root *gwou- "ox, bull, cow." Figurative sense of "inert and stupid" is from 1855.
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radon (n.)

the heaviest gaseous element, short-lived and radioactive, 1918, from German Radon, from radium (q.v.) + -on suffix of inert gases. The element was identified in radioactive decay of radium. Alternative name niton (from Latin nitens "shining") gained currency in France and Germany.

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krypton (n.)

inert gaseous element, 1898, coined by its discoverers (Sir William Ramsay and Morris W. Travers) from Greek krypton, neuter of adjective kryptos "hidden" (see crypt); so called because it remained undiscovered for so long and was so difficult to find. Scientific American (July 9, 1898) announced it as "the discovery of yet another element."

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argon (n.)
chemical element, 1894, Modern Latin, from Greek argon, neuter of argos "lazy, idle, not working the ground, living without labor," from a- "without" (see a- (3)) + ergon "work," from PIE root *werg- "to do." So called by its discoverers, Baron Rayleigh and Sir William Ramsay, for its inert qualities. They described it as "most astonishingly indifferent."
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