Not sure of the entymology (Sp) of the word Butty to describe as you say Paulie.......a sandwich!
Possibly to do with the butter on the sandwich that has become diluted to Bacon with Butter (Bacon Butty) Also, to share your food with a friend (Butty being an old British word for a mate, long gone and not used) at work, could be it........
Also, Butty may have become 'buddy' in the States also denoting a mate!
Bacon Buddy! - Bacon Mate?
I should be teaching English eh?
I would if it paid! 5555555 :erf: