I do know what you were talking about, I have family that live in Jersey.
I've heard from dubious sources that during the Civil War the southern part of New Jersey had a large number of Confederate sympathizers, and that many actually joined the Confederate Army.
I don't know if it's true, I've never found it in any history books. I just thought someone from Jersey may know something about the history that isn't exactly 'common knowledge'. That wasn't an 'old' joke nor was I confused by what you meant.
And no, Deliverance wasn't a true story, to the best of my knowledge.
Although; I do get a little nervous driving alone through deep back-woods and on dirt roads in 'hollers' (hollows, you Eastern Folk would call it a 'valley').
I have seen some wild looking folk in this state.
But I'd imagine I'd feel the same driving through Trenton, or Newark, or Camden.
Is Camden still in the Top 10 most dangerous cities list?
I'm pretty sure Detroit dethroned Camden as number 1.
Oh, and about us 'hillbillies'... you do know the 'tooth brush' was invented by a hillbilly, right?
Otherwise it would have been called a 'teeth brush'.