late 14c., persuasioun, "action of inducing (someone) to believe (something) by appeals to reason (not by authority, force, or fear); an argument to persuade, inducement," from Old French persuasion (14c.) and directly from Latin persuasionem (nominative persuasio) "a convincing, persuading," noun of action from past-participle stem of persuadere "persuade, convince," from per "thoroughly, strongly" (see per) + suadere "to urge, persuade," from PIE root *swād- "sweet, pleasant" (see sweet (adj.)).
Meaning "state of being convinced" is from 1530s; that of "religious belief, creed" is from 1620s. Colloquial or humorous sense of "kind, sort, nationality" is by 1864.