"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.

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

"small firearm with a curved handle, intended to be held in one hand when aimed and fired," 1570s, from French pistole "short firearm" (1566), a word of uncertain origin, sometimes said to be from German Pistole, from Czech pis'tala "firearm," literally "tube, pipe," from pisteti "to whistle," a word of imitative origin, related to Russian pischal "shepherd's pipe."

But the earlier English form pistolet (1550) is said to be from French pistolet "a small firearm," also "a small dagger," which is said to be connected with Italian pistolese, in reference to Pistoia, the town in Tuscany noted for gunsmithing.

Pistol-whip (v.) "strike (someone) with the butt of a pistol is recorded by 1942. Pistol-grip "handle shaped like the butt of a pistol" is by 1874.

"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.

also pistoleer, "one who uses a pistol, soldier armed with a pistol," 1570s from obsolete French pistolier, from pistole (see pistol).

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.

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.

1792, agent noun from equalize. Sports sense attested by 1930; in the U.S. underworld slang sense of "pistol," it is from c. 1900.

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

"sound of something moving rapidly," 1875, imitative. Zip gun "homemade pistol" is attested by 1950.