There are more than a few different legends concerning Caliburn. The sword has many various names with numerous spellings: Caliburnus, Caledfwlch, Calesvol, Calabrum, Callibourc, Chalabrun, Kaledvoulc'h and Calabrun (with alternate spellings such as Chalabrum, Calibore, Callibor, Caliborne, Calliborc, and Escaliborc and the names and legends are thought to descend from other famous swords such as: Caladbolg and Gram.
In some legends the two swords are the same and in others they are different. When they are different Caliburn is said to have been the sword in the stone, broken in battle when Arthur misused it to defeat Lancelot. Caliburn was the blade the made Arthur king and Excalibur was the blade that allowed him to keep his kingship.
In some stories and legends the blades had writing upon their fuller. Upon Caliburn was written: "Whoso pulleth out this sword of this stone and anvil is rightwise king born of all England." Upon one side of Excalibur was written: "Take me up." Upon the other side was written: "Cast me away."
Though not named as Caledfwlch (Caliburn), Arthur's sword is described vividly in The Dream of Rhonabwy one of the tales associated with the Mabinogion. It is likely this sword is Caliburn as the story is placed shortly after Arthur became king.
"Then they heard Cadwr Earl of Cornwall being summoned, and saw him rise with Arthur's sword in his hand, with a design of two chimeras on the golden hilt; when the sword was unsheathed what was seen from the mouths of the two chimeras was like two flames of fire, so dreadful that it was not easy for anyone to look. At that the host settled and the commotion subsided, and the earl returned to his tent."
Nineteenth century poet Alfred, Lord Tennyson, described the sword in full Romantic detail in his poem "Morte d'Arthur", later rewritten as "The Passing of Arthur", one of the Idylls of the King. Excalibur is named in this poem.
"There drew he forth the brand Excalibur,
And o’er him, drawing it, the winter moon,
Brightening the skirts of a long cloud, ran forth
And sparkled keen with frost against the hilt:
For all the haft twinkled with diamond sparks,
Myriads of topaz-lights, and jacinth-work
Of subtlest jewellery."