A welsh insult deriving from ancient welsh folklore. An endaf is a disgusting creature that lurks in the dark, most of the time eating mold underneath cabbage plantations. It is the only creature horrendously grotesque enough to be classed as a runt in the animal kingdom. Do not touch its boils as it enjoys it.
"Hey you look bad today mate, bit of an endaf!"
"Ahaha maate i was so drunk lastnight i smashed an endaf!"