c.1200, belwes, literally "bags," plural of belu, belw, northern form of beli, from late Old English belg "bag, purse, leathern bottle" (see belly (n.)). Reduced from blæstbælg, literally "blowing bag." Used exclusively in plural since 15c., probably due to the two handles.
occurs only in Jer. 6:29, in relation to the casting of metal. Probably they consisted of leather bags similar to those common in Egypt.