I am the lady u kindly sent info to last year.I am still trying to find some conclusive proof for the origin of the surname.Another colleague sent some info also on the book Lancashire legends in the extract it mentions the local Monks kept tithe or such records which record the name Ayndoles etc.. I have the parish records of Formby here on Fiche now going back to the early 1600's the first name of the name in the parish records seems to be "Aynsdell" somewhere I have a reference to a Richard of Aynsdale mentioned back in the 13th century.
So far I have been unable to find like yrself the true origin but the book Lancashire Legends does seem to have the most realistic reason as to why the surname is very local to the Formby area.
I will keep looking in the hope we find out one day!!