1510s, "a talk," from Latin sermonationem (nominative sermonatio), noun of action from past participle stem of sermonari "talk, discourse, harangue," from sermo (see sermon). From 1753 in rhetoric, "a form of prosopopoeia in which the speaker, having addressed a real or imaginary hearer with a remark or especially a question, immediately answers for the hearer." Related: Sermocinator, agent noun; sermocinatrix "a female talker" (1620s).