Hoël, Hoelus, Hoïlas
Several kings or lords of Britain or Brittany (usually clearly identified as the latter), or of Breton cities, are given this name in a number of Arthurian texts: Geoffrey of Monmouth’s Historia Regum Britanniae (as Hoelus), Wace’s Brut, Marie de France’s Guigemar (as Hoïlas), the Vulgate Suite du Merlin, and Renaut de Beaujeu’s Le Bel Inconnu.
According to the Tristan tradition, King Hoël of Brittany is the father of Iseult White-Hands and Kahedin; this is probably true as well in the lost parts of Thomas’s Tristan, and in the Prose Tristan and those romances influenced by it. In the chronicles, Hoël is usally a cousin of Arthur.
A ruler named Hoel govered Brittany in the time of William of Conqueror and was one of William’s allies. Geoffrey of Monmouth may have adopted Hoel’s name in order to flatter his Norman patrons.