rai|son|neur

rai|son|neur «reh z NERR», noun.

a character, especially in a play or novel, who rationalizes, explains, or comments upon the actions of the other characters: »

Ferdyshenko…is brought on [in a stage production of Dostoevsky's “The Idiot”] as a guide and raisonneur, to nudge, chuckle and underline such points as have been elaborated before our eyes (Manchester Guardian Weekly).

╂[< French raisonneur reasoner, rationalizer]