... The stronghold of Eurnach or Urnach is said to have been Dinas Ffaraon, which was afterwards called Din Emreis and Dinas Emrys.  The whole story about the Goidels in North Wales, however, as given in the Iolo MSS., pp. 78-80, is a hopeless jumble, though it is probably based on old traditions.  In fact, one detects Eurnach or Urnach as Wrnach or Gwrnach in the story of Kulhwch and Olwen in the Red Book, where we are told that Kei or Cai, and others of Arthur's men, got into the giant's castle and cut off his head in order to secure his sword, which was one of the things required for the hunting of Twrch Trwyth.  In an obscure passage, also in a poem in the Black Book, we read of Cai fighting in the hall of this giant, who is then called Awarnach... (Celtic Folklore: Welsh and Manx, Rhys, v.2, 1901)