Actually Catherine Bronte was responsible for the switch when she gave the name to one of her female characters.
Shirley was originally one of those surnmme given to the first-born son as a first name when a heiress married. (eg in Pride and Prejudice Fitzwiiliam Darcy's mother's maiden name was orginally Fitzwilliam)
So when Miss Jane Shirley married Mr John Sirius, their fisrt borm son might end up being named Shirley Sirius.
Thanks! Great to find out how that came about.
There had to be a Miss Jane Howlin who married Mr. John Wolf. Right?
"Shirley Sirius."
Surely you're not!