I think it's British slang for grapes. He's saying your dad is a wineo!!
He stole that from Monty Pythons Quest for the Holy grail. Unoriginal !!! you get minus points for that!!
It was an obvious culture reference, anyone who has seen monty python's quest for the holy grail knows that insult. The fact it wasn't original was a part of the point. I mean, I could insult people originally, like I could say that your parents should have spent the money to get a real pinata and not used you as we all suffer today from your brain damage. I could even go on some spiteful tyrade about how you are a cocksucking faggot who makes Forrest Gump look like Einstein. Frankly though, culture references are easy to get, accept, and use to find common ground.