Sure it wasn't Susan's Candy Store and your Grandpa had some teeth missing?
Seriously, though. Your mother's surname is quite unusual and it may interest you that there was a Geoff Mulcahy (pronounced Mulk-eye) at Worcester Cathedral King's school here in England during the 50/60s. After he left school Geoffrey went on to become the Chief Executive Officer of the Kingfisher Group which, among many other chains, owns The Woolworths Group.
You never know, perhaps you're related.