KW Keller writes...

Well, I'm not Todd, but in response to the history of Excalibur, Geoffrey of Monmouth's "Caliburn" is thought by some to be derived from the Welsh "Caledfwlch" (Breton "Kaledvoulc'h"), or from the Irish "Caladbolg" or "Caladcholg." Caledfwlch appears in several Welsh Arthurian stories, especially "Culhwch ac Olwen." Caladbolg, "hard dinter," was the lightning sword of Fergus Mac Roth. Caladcholg was a similar sword owned by Fergus Mac Leti. Various people have argued at one time or another that the modern idea of Excalibur was taken from one of these sources.