FROCK, originally a long, loose gown with broad sleeves, worn by members of the religious orders. The word is derived from the O.Fr. froc, of obscure origin. The formal stripping off of the frock became part of the ceremony of degradation in the case of a condemned monk; hence the expression "to unfrock." In the middle ages "frock" was also a long loose coat worn by men, or a coat of mail, and the word survived into the 19th century for a coat with long skirts, the "frock coat." It is now chiefly used in English for a child's or young girl's dress.