Instead of a detailed description of this topic, I'm going to post a variety of links. In some versions of the legend of the "melon heads" are actually children with Hydrocephalus, but in others they are not. The legend dates back to before there was modern shunt technology so at that point it often went untreated. In a way I can see how some of the character traits of the melon heads may have been seen in people with untreated Hydrocephalus, which of course was exaggerated. I'm sure that it was insulting then but now that the description of the melon heads doesn't even come close to most who live with Hydrocephalus. I saw a pretty accurate of Hydrocephalus although vague on several sites there's no mention of current treatment and ways of life, so it could give people a bad description of people living with the condition. Even if they look more into it, or know someone with it, it might make them believe that's what we're like at least in a way, no matter what.