1919, from Pa. Dutch dunke "to dip," from M.H.G. dunken, from O.H.G. dunkon, thunkon "to soak," from PIE base *teng- "to soak" (see tincture
). Basketball sense is first recorded 1937. German-American Anabaptist sect of Dunkers (who baptize with triple immersion) first recorded by that name 1756.