As a curious fact him does not have a name but they simply call him "5" due to a tattoo on his arm since the "7 wonders" that are the stars of the circus (Stace would be 7) have a number tattooed somewhere on his body so since they don't remember their names they simply call each other by the number they have tattooed

I don't know if I explained it well but I think you understand the idea xd