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Old English spearca, from Proto-Germanic *spark- (cf. Middle Low German sparke, Middle Dutch spranke, not found in other Germanic languages). Electrical sense dates from 1748. Slang sense of "a gallant, a beau, a lover" (c.1600) is perhaps a figurative use, but also perhaps from cognate Old Norse sparkr "lively." Spark plug first recorded 1903 (sparking plug is from 1902); figurative sense of "one who initiates or is a driving force in some activity" is from 1941.
c.1300, from spark (n.). Slang meaning "stimulate, to trigger" first attested 1912. Related: Sparked; sparking.