There are many different variations of this name.
I have a page on it on my website at:
http://www.irishmcgoff.com/Hehirs/history%20of%20the%20name%...

Also, I've got ship lists lists of Hehir's where
persons in the same family have their names spelled
differently.

I hope this helps,
Michelle McGoff
http://www.irishmcgoff.com