Why is the ninth month called September?
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).
ground beef. The term is applied variously to (1) a patty of ground beef, sometimes called hamburg steak, Salisbury steak, or Vienna steak, (2) a sandwich consisting of a patty of beef served within a split bread roll, with various garnishes, or (3) the ground beef itself, which is used as a base in many sauces, casseroles, terrines, and the like. The origin of hamburger is unknown, but the hamburger patty and sandwich were probably brought by 19th-century German immigrants to the United States, where in a matter of decades the hamburger came to be considered an archetypal American food. The importance of the hamburger in American popular culture is indicated by its virtual ubiquity at backyard barbecues and on fast-food restaurant menus and by the proliferation of so-called hamburger stands and restaurants. Some chains, such as McDonald's, Burger King, and Wendy's, proliferated worldwide.