NECKBEARD MODE ENGAGED
Caliburn and Excalibur are the same sword. This same sword also shows up in Irish myth as Caladbolg aka Caladcholg or Caladwlch held by Fergus McRoy. Before him it was wieded by Mannanan McLyr, god of the sea, and after Fergus died the sword returned to the water.
The sword is also part of a set of items taken by the Daanan (the fey) from the 4 cities of their homeland. The sword came from the city of Gorias. Also the cauldron of Murias, the spear of Finias, and the Lia Fail or stone of Falias.
Fun fact, the Lia Fail was used in the coronation of Irish kings until the Scots took it. From them it was taken by the English. It is now known as the Stone of Scone.