Is it ensure, insure, or assure?
1610s, "native of Hamburg;" the meat product so called from 1884, hamburg steak, named for the German city of Hamburg, though no certain connection has ever been put forth, and there may not be one unless it be that Hamburg was a major port of departure for German immigrants to United States. Meaning "a sandwich consisting of a bun and a patty of grilled hamburger meat" attested by 1912. Shortened form burger attested from 1939; beefburger was attempted 1940, in an attempt to make the main ingredient more explicit, after the -burger had taken on a life of its own as a suffix (cf. cheeseburger, first attested 1938).