headcanon (hed-can-un) noun. - A believed idea or concept of a story that is conjured by a fan to fit in with or otherwise explain various aspects in the story. While not directly expressed in-canon, these ideas can be generally accepted by the fandom.
Peter Sutcliffe was known as the Yorkshire ripper. He went around killing women in the most cruelest ways. It was said that having a pencil through his eye and glass ground into his food could finish him off in hopes of shredding his bowels