c.1400, "wooden siege tower on wheels" (late 13c. in Anglo-Latin with a sense "bell tower"), from Old North French berfroi "movable siege tower" (Modern French beffroi), from Middle High German bercfrit "protecting shelter," from Proto-Germanic compound *berg-frithu, literally "high place of security," or that which watches over peace." From bergen "to protect" (see bury) or *bergaz "mountain, high place" (see barrow, n.2) + *frithu- "peace; personal security" (see affray). It came to be used for chime towers (mid-15c.), which at first often were detached from church buildings (as the Campanile on Plaza San Marco in Venice). Spelling altered by dissimilation or by association with bell (n.).