"5-gallon metal container," 1943, from Jerry "a German." It was first used by German troops in World War II and later adopted by the Allies.
Entries linking to jerry-can
Jerry n.
World War I British Army slang for "a German; the Germans," 1919, probably an alteration of German based on the male nickname Jerry, popular form of Jeremy. But it also is said to be from the shape of the German helmet, which was thought to resemble a jerry, British slang for "chamber pot, toilet" (1850), this being probably an abbreviation of jeroboam, which is attested in this sense from 1827. Compare jerry-hat "round felt hat" (1841).