identity (n.)
c. 1600, "sameness, oneness, state of being the same," from Middle French identité (14c.), from Medieval Latin identitatem (nominative identitas) "sameness," ultimately from Latin idem (neuter) "the same" (see idem). [For discussion of Latin formation, see entry in OED.] Earlier form of the word in English was idemptitie (1560s), from Medieval Latin idemptitas. Term identity crisis first recorded 1954. Identity theft attested from 1995.