A wrong'un is a slang term for a person who is dishonest or disreputable, or a cricketing term for a googly.
He rammed her up the wrongun
Robbie Dalton made the "Dogface" See this link DO NOT TRY TO CONTACT BUICKSMASHER, HE RIPPED OFF A COUPLE OF PALS OF MINE, HE'S A WRONGUN NONCE!!!!! http://www.theknifeauction.com/item.php?id=50794 Hope this helped:-)