haley bop is a nickname her family gaver her...she doesnt have a middle name, at least she ddn until she got married and then her maiden name became her middle name...hope that helps :)
Her middle name is bob because before her parents had kids they had a tabby cat named bob who was stubborn and squirmy and didn't like to be held. When Haley was born she too was squirmy and her mother said "she's squirmyband stubborn just like Bob" so they named her Haley Bob James. Shes named after a cat. S08E18
well she is Haley Bob James Scott. her family calls her HaleyBob for an unknown reason. for example Quinn has done it several times in all her epis so far. also the deleted scene when the girls were arrested in S3, her name had the middle initial B. so for sure its her legal middle name, not just a family nickname. but we have never been told why they gave her that name.
