- expound c.1300, from O.Fr. espondre "expound (on), set forth, explain," from L. exponere "put forth, explain, expose, exhibit," from ex- "forth" (see EX- (Cf. ex-)) + ponere "to put, place" (see POSITION (Cf. position)); with intrusive -d (Cf. SOUND (Cf. sound) (n.1)). The usual M.E. form was expoune. Related: Expounded; expounding.
Etymology dictionary. 2014.