1851, "blind alley," from French impasse "impassable road, blind alley, impasse," from assimilated form of in- "not, opposite of" (see in- (1)) + Middle French passe "a passing," from passer "to pass" (see pass (v.)). Supposedly coined by Voltaire as a euphemism for cul de sac. Figurative use also from 1851.
