King Mob was a villain. He used to wear an ape mask. He was apprehended by the Minutemen and his mask was put as a trophy in their display room.
While the supervillain may have been trying to combine the images of King Kong and a mob boss, the name King Mob was originally used by rioters in England to refer to mob law. It is also the code name of two anarchist mystics in Grant Morrison's comic The Invisibles.