c. 1400, in law, "to charge, allege," from Old French surmis, past participle of surmettre "to accuse," from sur- "upon" (see sur- (1)) + mettre "put," from Latin mittere "to send" (see mission). Meaning "to infer conjecturally" is recorded from 1700, from the noun. Related: Surmised; surmising.