machine part, 1745, apparently from tap (v.1) + -et, "but the use of the suffix is abnormal" [OED].
"military engine for hurling stones," mid-13c., from Old French mangonel "catapult, war engine for throwing stones, etc." (Modern French mangonneau), diminutive of Medieval Latin mangonum, from Vulgar Latin *manganum "machine," from Greek manganon "any means of tricking or bewitching," said to be from a PIE *mang- "to embellish, dress, trim" (source also of Old Prussian manga "whore," Middle Irish meng "craft, deception"), but Beekes thinks it might be Pre-Greek. Attested from c. 1200 in Anglo-Latin.
1640s, "person who begets, causes, or produces," from Latin generator "a begetter, producer," agent noun from past participle stem of generare "to bring forth" (see generation). Meaning "machine that generates power" first recorded 1794; sense of "machine that generates electric energy" is from 1879. Fem. generatrix attested from 1650s.
1953, from Japanese, "pinball machine," also "slingshot, handgun," from pachin, of echoic origin, + diminutive suffix -ko.