idiosyncrasy

First attested in 1604, in modern sense since 1665, from Ancient Greek ἰδιοσυγκρασία (idiosunkrasía, “one’s own temperament”), from ἴδιος (ídios, “one’s own”) + σύν (sún, “together”) + κρᾶσις (krâsis, “temperament”). By surface analysis, idio- + syn- + -crasy.