Having lived in the south (Tennessee and North Carolina) most of my life, I haven't heard that one. I can believe is coming from a heavy southern accent sounding like "dope" instead, though. People are strange, nonetheless.

Before I was born, the majority of my family made a move from Iowa to Illinois to Tennessee (A weird transition on its own.) My brother almost got in trouble with a fast food chain when he ordered some "pop". The cashier misheard and thought he was asking for some pot and freaked out. (It didn't help he was a teenager at the time.) Nowadays, I think he's given up and conformed to just saying "coke".

According to the article, they call it that in the Carolinas.