Etymology
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weapon (n.)

Old English wæpen "instrument of fighting and defense, sword," also "penis," from Proto-Germanic *wēipna- (source also of Old Saxon wapan, Old Norse vapn, Danish vaaben, Old Frisian wepin, Middle Dutch wapen, Old High German wafan, German Waffe "weapon"), a word of unknown origin with no cognates outside Germanic; possibly a substratum word.

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automatic (adj.)

"self-acting, moving or acting on its own," 1812 (automatical is from 1580s; automatous from 1640s), from Greek automatos of persons "acting of one's own will;" of things "self-moving, self-acting," used of the gates of Olympus and the tripods of Hephaestus (also "without apparent cause, by accident"), from autos "self" (see auto-) + matos "thinking, animated" (from PIE root *men- (1) "to think").

Of involuntary animal or human actions, from 1748, first used in this sense by English physician and philosopher David Hartley. The meaning "done by self-acting machinery" is by 1850. In reference to a type of firearm, from 1877; specifically of machinery that imitates human-directed action from 1940.

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automatic (n.)

1902, "automatic weapon," from automatic (adj.). The meaning "motorized vehicle with automatic transmission" is from 1949.

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semi-automatic (adj.)

"partially automatic," 1853, from semi- + automatic (adj.). In reference to a firearm that loads all or partly by itself (but does not fire continuously) by 1889. As a noun in this sense (short for semi-automatic firearm, etc.) by 1964.

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automatize (v.)

1837, "to make into an automaton, make into a self-acting machine;" see automaton + -ize. The meaning "to make automatic" is attested by 1952 (see automatic (adj.)). Related: Automatized; automatizing.

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Instamatic 

1962, proprietary name (reg. Eastman Kodak Co., Rochester, New York) for a type of self-loading camera, from instant + automatic.

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automation (n.)

1948, in the manufacturing sense, "the large-scale use of automatic equipment in production," coined by Ford Motor Co. Vice President Delmar S. Harder, from automatic (adj.) + -ion. Earlier (1838) was automatism, which meant "quality of being automatic" in the classical sense.

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Luger (n.)

type of German automatic pistol, 1904, from the surname of Georg Luger (1849-1923), Austrian-born firearms expert.

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thermograph (n.)

"automatic self-registering thermometer," 1881, from thermo- + -graph "instrument for recording; something written." Related: Thermographic.

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Luftwaffe 

air arm of the German Wehrmacht in the World War II era, 1935, from German Luftwaffe, literally "air-weapon," from Luft (see loft (n.)) + Waffe (see weapon (n.)).

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