A vintage cartoon of two boys and a man. One of the boys is fat and says, “Whew! That’s over! But I’m as weak as a cat!” The adult wearing a red T-shirt with a yellow letter T on it says, “Have a Tootsie Roll, Fatso! It will give you added energy, quick!”
I’m not sure if that makes it better or worse. If they were a real person it would be better. But being that it’s a fictional character, it means the writters named him “Fatso”.
the whole thing was advertisements for tootsie roll candies. so the name ‘fit’, i guess.