But...but..I thought Europe was an illiterate wasteland, save only for "Spain". How dare those benighted Welsh produce a history?
Yes, I am aware of the Welsh threads in the Arthurian legend, through such links as the Annals and the Mabinogion's Red Book and White Book. Still the core of the Arthur stories, the Grail Quest, Lancelot and Camelot, started with the Troubadors. Specifically, with Chretien de Troyes.
The Annals didn't mention Merlin (Myrrdin). He was the addition of Geoffrey of Monmouth.
Geoffrey of Monmouth is believed to have invented the FORM of the name, not the name itself. He was originally called EMRYS.