on the wagon

Etymology:

• Originally on the water wagon or on the water cart, referring to carts used to hose down dusty roads: see the 1901 quotation below. The suggestion is that a person who is “on the wagon” is drinking water rather than alcoholic beverages. The term may have been used by the early 20th-century temperance movement in the United States; for instance, William Hamilton Anderson, the superintendent of the New York Anti-Saloon League, is said to have made the following remark about Prohibition: “Be a good sport about it. No more falling off the water wagon. Uncle Sam will help you keep your pledge.”