Chunder means to be sick, it originates from old seafareing days when sailers would get seasick and stick their head out of the porthole in their cabin. As they did this they would shout "Watch Under" to warn people in lower cabins of the forthcoming puke. Over the years this has evolved in Chunder.
Peodophiles are sick, they make me want to Chunder!
James: What the fuck is that on your leg?
Anthony: I don't know, I've had it for about six months, it doesn't hurt though.
James: I'd go to the Doctors if I were you. It looks like Ringworm.
Anthony: Ringworm! But that's what dirty bastards get.
James: And your point is?