I know that Efrawg sounds perfectly Welsh, but it’s actually just the British version of Latin Eboracum, modern York. Now that’s a little odd for a man’s name, but then again it isn’t actually a man’s name. You see there actually was an historical Peredur. His father’s name was Eliffer and most scholars locate him around York. See how that works, Peredur was from York so his patronym was mistakenly mixed up with the area he ruled.