mid-15c., pestiferus, "bringing plague, plague-bearing, pestilential," also in a weakened or figurative sense, "mischievous, malignant, pernicious, hurtful to morals or society," from of Latin pestiferus "that brings plague or destruction," variant of pestifer "bringing plague, destructive, noxious," from pestis "plague" (see pest) + ferre "carry," from PIE root *bher- (1) "to carry," also "to bear children." Related: Pestiferously; pestiferousness.