Early 17th century. From post-classical Latin adiaphorus (in prosody, of syllables) optionally short or long, of variable quantity, (in philosophical or religious context) indifferent, (of a medicinal agent) neither harmful nor beneficial or its etymon ancient Greek ἀδιάϕορος not different, (in Stoic philosophy) indifferent, neither good nor bad, in Hellenistic Greek also (in prosody, of syllables) optionally short or long, of variable quantity + -ous. Compare German adiaphorisch, French adiaphore.