Noun: A misguided aspect of self that repeatedly leads us down self-destructive pathways. It is formed in childhood by factors such as trauma and messaging and resurfaces as dysfunctional repetitive behavior. 

Origin: the concept “Traitor Within” was created by Jessica Anne Pressler LCSW, to give people a tangible and workable tool to help identify and overcome their repetitive self-sabotaging behavior. It is also the title of her book.