1948, in the manufacturing sense, 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.
"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," *men- (1) "to think."
Of involuntary animal or human actions, from 1748, first used in this sense by English physician and philosopher David Hartley. 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.
word-forming element attached to verbs, making nouns of state, condition, or action, from French -ion or directly from Latin -ionem (nominative -io, genitive -ionis), common suffix forming abstract nouns from verbs.