Clipped from hamburger, named after Hamburg, Germany — the ham- prefix has nothing to do with ham.
A flat round cake of minced meat served in a bread roll.
Shortened from hamburger, from Hamburg, Germany's second-largest city. The hamburger steak (a patty of ground beef) was likely brought to America by German immigrants. The word was then clipped to 'burger' and reanalyzed as ham-burger, spawning cheese