1610s as a term in logic; general sense of "being the same or very similar" is from 1630s, from Medieval Latin identicus "the same," from Late Latin identitas "identity, sameness," ultimately from combining form of Latin idem "the same" (see idem). Replaced Middle English idemptical (late 15c.), from Medieval Latin idemptitas "identity," from Latin idem. Related: Identically.
updated on October 09, 2017