It's a Nazareth song. Axl has said it was the singer from Nazareth who made him want to sing the way he does. I saw them back in the Summer of 2000 in Canada, it was the night I proposed to my wife. They played that song as well as a shit load of other of thier songs (Fallen Angel, Hair of the dog and Broken down angel were probably the best songs on the night). A great band to see live if you can.
Scree
If you can't see them live I would buy the "Back To The Trenches" Live 2 CD album. It's amazing. Early Nazareth at their best.