how does piggy nickname and physical description potentially move the plot early in the novel?

We find out that the "fat boy" has a name: it is Piggy. This, of course, is not his real name which makes the irony all the more painful when he is killed and still don't know his name. Piggy's early confessional to Ralph, about his name, movers the narrative into the psychology of pre-adolescent boys. The boys know each other for their physicality (Bigguns, Littluns, fair boy, fat boy....) and are defined by their childish preconceptions about the value that individuals might have. Piggy is seen as a symbol of intelligence and weakness to be mocked. Ralph, having the shoulders of a boxer, commands a certain respect without having to say much at all. This sets the tone of the narrative for the rest of the novel.