Etymology
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armor (n.)
c. 1300, "mail, defensive covering worn in combat," also, generally, "means of protection," from Old French armeure "weapons, armor" (12c.), from Latin armatura "arms, equipment," from arma "weapons" (including defensive armor), literally "tools, implements (of war)," see arm (n.2). Figurative use from mid-14c.

Meaning "military equipment generally," especially siege engines, is from late 14c. The word might have died with jousting if not for 19c. transference to metal-sheathed combat machinery beginning with U.S. Civil War ironclads (it is first attested in this sense in an 1855 report from the U.S. Congressional Committee on Naval Affairs). Meaning "protective envelope of an animal" is from c. 1600.
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breakdown (n.)

also break-down, 1832, "a collapse, a falling apart," from the verbal phrase (attested by late 14c. in the sense "take down by breaking" (trans.); 1831 in the intransitive sense "come down by breaking; 1856 as "to fail through incapacity, excess emotion, etc."); see break (v.) + down (adv.). The noun, specifically of machinery, is from 1838; meaning "an analysis in detail" is from 1936 (from the verbal phrase in the sense "analyze, classify," 1934). Also in 19c. American English "a noisy, lively dance sometimes accompanied by singing" (1864). Nervous breakdown is from 1866.

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mechanic (n.)

1560s, "one who is employed in manual labor, one who works mechanically, a handicraft worker, an artisan," from Latin mechanicus "of or belonging to machines or mechanics," from Greek mekhanikos "an engineer," noun use of adjective meaning "full of resources, inventive, ingenious," from mēkhanē "device, tool, machine; contrivance, cunning" (see machine (n.)).

Their social and professional organizations were prominent late 18c. and early 19c. in Britain and America, and account for the Mechanics Halls in many towns and the Mechanicsvilles and Mechanicsburgs on the map. The sense of "skilled workman who is concerned with the making or repair of machinery" is attested from 1660s, but was not the main sense of the word until the rise of the automobile in late 19c.

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idle (adj.)

Old English idel "empty, void; vain; worthless, useless," from Proto-West Germanic *idla- (source also of Old Saxon idal, Old Frisian idel "empty, worthless," Old Dutch idil, Old High German ital, German eitel "vain, useless, mere, pure"), a word of unknown origin.

Subsequent developments are peculiar to English: sense "not employed, not doing work" was in late Old English in reference to persons; from 1520s of things; from 1805 of machinery. Meaning "lazy, slothful" is from c. 1300. In Elizabethan English it also could mean "foolish, delirious, wandering in the mind." Idle threats preserves original sense.

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treadmill (n.)

invented (and named) 1822; originally an instrument of prison discipline; from tread (v.) + mill (n.1). Treadwheel as a similar method of driving machinery is from 1570s.

As a corrective punishment, the discipline of the stepping mill has had a most salutary effect upon the prisoners, and is not likely to be easily forgotten, while it is an occupation which by no means interferes with, nor is calculated to lessen the value of, those branches of prison regulation which provide for the moral and religious improvement of the criminal. ["Description of the Tread Mill Invented by Mr. William Cubitt of Ipswich for the Employment of Prisoners," London, 1822]

By later generations regarded as a path to physical fitness.

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reservoir (n.)

1680s, "a place where something tends to collect, place where anything is kept in store," originally figurative, from French réservoir "storehouse," from Old French reserver "set aside, withhold," from Latin reservare "keep back, save up; retain, preserve," from re- "back" (see re-) + servare "to keep, save, preserve, protect" (from PIE root *ser- (1) "to protect").

Specific meaning "capacious artificial basin to collect and store water" is from 1705. Earlier in this sense, and more common late 17c.-early 18c., was reservatory (1660s). Meaning "part of a machinery in which fluid is contained" is by 1784.

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engage (v.)

early 15c., "to pledge" (something, as security for payment), from Old French engagier "bind (by promise or oath), pledge; pawn" (12c.), from phrase en gage "under pledge," from en "in" (see en- (1)) + gage "pledge," through Frankish from Proto-Germanic *wadiare "pledge" (see wed). It shows the common evolution of Germanic -w- to central French -g- (see gu-).

Meaning "attract and occupy the attention of" is from 1640s; that of "employ, secure for aid, employment or use" is from 1640s, from notion of "binding as by a pledge;" meaning "enter into combat or contest with" is from 1640s. Specific sense of "promise to marry" is 1610s (implied in engaged). Machinery sense is from 1884. Also from the French word are German engagiren, Dutch engageren, Danish engagere.

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carriage (n.)
late 14c., "act of carrying, means of conveyance; wheeled vehicles collectively," from Anglo-French and Old North French cariage "cart, carriage, action of transporting in a vehicle" (Old French charriage, Modern French charriage), from carier "to carry," from Late Latin carricare, from Latin carrus "two-wheeled wagon" (see car).

Meaning "individual wheeled vehicle" is c. 1400; specific sense of "horse-drawn, wheeled vehicle for hauling people" first attested 1706; extended to railway cars by 1830. Meaning "the business of transportation" is from 1520s. Meaning "way of carrying one's body" is 1590s, hence also "behavior, conduct, manners." Sense of "a part of a machinery which carries another part" is from 1680s. Carriage-house attested from 1761.
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chamber (n.)

c. 1200, "a room in a house," usually a private one, from Old French chambre "room, chamber, apartment" (11c.), from Late Latin camera "a chamber, room" (see camera).

The Old French word and the Middle English one also were used alone and in combinations to form words for "latrine, privy" from the notion of "bedroom utensil for containing urine." In anatomy, "enclosed space in a body," from late 14c. Of machinery, "artificial cavity," from 1769. Gunnery sense "part of the bore in which the charge is placed" is from 1620s. Meaning "legislative body" is from c. 1400, an extended sense from the chambers or rooms where an assembly meets. Chamber music (1765) traditionally was that meant to be performed in smaller spaces.

DA CAMERA: of the chamber, i. e. belonging to the chamber, suitable for the chamber, designed for the chamber,—a term applied to parlor or chamber music. [Godfrey Weber's General Music Teacher," Boston, 1842]
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ream (v.)

"to enlarge a hole," especially "to widen or enlarge by the use of a rotary cutter," 1815, a word of "somewhat doubtful origin" [OED], but it is probably a southwest England dialectal survival from obsolete Middle English reme "to make room, open up, extend by stretching."

This is from Old English ryman "widen, extend, enlarge," from Proto-Germanic *rumijan (source also of Old Saxon rumian, Old Norse ryma, Old Frisian rema, Old High German rumen, German räumen"to make room, widen"), from *rumaz "spacious" (see room (n.)). Related: Reamed; reaming; reamer.

Especially with out (adv.). The slang meaning "to cheat, swindle" is recorded by 1914; the sexual sense is attested by 1942. To ream (someone) out in the sense of "to scold, reprimand" is recorded from 1950; earlier it was used of gun barrels, machinery, etc., "to remove (a jam or defect) by reaming" (1861).

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