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1796, from French incroyable, literally "incredible" (15c.), from in- "not, opposite of, without" (see in- (1)) + croire "to believe," from Latin credere (see credo). Name for the French fop or dandy of the period of the Directory (1795-99). Said to be so called from their extravagant dress and from a favorite expression among them ("C'est vraiment incroyable").