An abbreviation for fat soul. This commonly used insult is more than a mere comment on a person’s physical appearance. It refers to the inner motivations behind this person’s gluttony, hinting that the unstoppable craving for food is a integral part of his or hers personality, or soul. Thus a fatso need not be a obese son of a bitch that has to pay for two seats on an airplane, but might as well be skinny like that most hospitable of Hilton hotels.
Burger joint employee: Do you want the extra large menu for only 1$ extra?
Fatso : Damn man! Look at me! What the hell do you think???