Where did Excalibur come from?

excaliber was given to King Arthur by the lady of the lake.

it is said that he took his sWord and attacked a innocent knight and his sWord shattered. after this king Arthur needed a sWord so Merlin took him to see the lady of the lake. at the lake there was a hand protruding from the surface holding excaliber. Merlin and Arthur rode a raft to the hand and got the sWord.