BILGE (a corruption of bulge, from Fr. bouge, Lat. bulga, a bag, deriving probably from an original Celtic word), the " belly " or widest part of a cask; the broad horizontal part of a ship's bottom above the keel; also the lowest interior part of the hull; hence " bilge-water," the foul water which collects in the bilge. " Bilge-keels " are pieces of timber fastened to the bottom of a ship to reduce rolling (see SHIPBUILDING).