Belfredus, is used by military writers of the middle ages to denote a tower erected by besiegers to overlook the place besieged. Sentinels were placed on the belfry to watch the avenues and prevent surprise, or to give notice of fires by ringing a bell. The word belfry is compounded of the Teutonic bell, and freid, "peace." Belfry also denotes that part of a steeple in which the bells are hung; sometimes called by old writers campanile, cloacaria, and tristegium.