Every time I see that post about how Excalibur and Caliburn are different swords, and Excalibur is the sword given by the Lady in the Lake, and Caliburn is the sword in the stone, I just sit there shaking my head, because everyone on it is so earnest, and certain of their rightness, and frustrated with everybody else being Wrong about Arthurian myth, and they are all just as wrong as the people they are trying to correct.
Excalibur and Caliburn are two words for the same sword, both derived from the Welsh Caledfwlch. Caliburn (or Caliburnus) is the Latinization, and Excalibur is the Old French version. Sometimes this sword is the sword in the stone, and sometimes it’s given by the Lady in the Lake. Sometimes there is a sword in the stone, and sometimes there isn’t. Sometimes there is a Lady in the Lake and sometimes there isn’t. Arthurian myth, like all myths, doesn’t have a single definitive version. It’s a grab bag of many related stories told by many different people, that don’t fit together into any kind of cohesive whole, and that often contradict each other. Every one of us gets to pick the bits and pieces to stitch together into the version we like best.
So Excalibur and Caliburn can be two different swords, or one sword. There can be a sword in the stone, or a Lady in the Lake, or both. It’s up to you. And no one version is the right one, but also none of them are wrong.