late 14c., from Old French suasion (14c.) and directly from Latin suasionem (nominative suasio) "a recommending, advocacy, support," noun of action from past participle stem of suadere "to urge, incite, promote, advise, persuade," literally "recommend as good" (related to suavis "sweet"), from PIE *swad- "sweet, pleasant" (see sweet (adj.)). Survives chiefly in phrase moral suasion (1640s). Latin Suada was the goddess of persuasion.
