What is the X in X-mas?
fem. proper name, from Welsh Gwenhwyvar, literally "white-cheeked."
wife of Arthur, legendary king of Britain, best known in Arthurian romance through the love that his knight Sir Lancelot bore for her. In early Welsh literature, one Gwenhwyvar was "the first lady of this island"; in Geoffrey of Monmouth's inventive Historia regum Britanniae (early 12th century), she was named Guanhumara and was presented as a Roman lady. In some accounts it was suggested that she was Arthur's second wife.