Excalibur
Geoffrey of Monmouth, in his "Historia Regum Britanniae" ("The History of the Kings of Britain", c. 1136), Latinised the name of Arthur's sword as "Caliburnus" (potentially influenced by the Medieval Latin spelling "calibs" of Classical Latin "chalybs", from Greek "chályps" ["χάλυψ"] "steel"). Most Celticists consider Geoffrey's "Caliburnus" to be derivative of a lost Old Welsh text in which "bwlch" (Old Welsh "bulc[h]") had not yet been lenited to "fwlch" (Middle Welsh "vwlch" or "uwlch"). In the late 15th/early 16th-century Middle Cornish play "Beunans Ke", Arthur's sword is called "Calesvol", which is etymologically an exact Middle Cornish cognate of the Welsh "Caledfwlch". It is unclear if the name was borrowed from the Welsh (if so, it must have been an early loan, for phonological reasons), or represents an early, pan-Brittonic traditional name for Arthur's sword.
Artus-Excalibur
Some time later, countless people, including a grown Arthur and his adoptive father, Sir Ector, gather around the stone to see if someone can pull free Excalibur ("Excalibur"). Arthur does not believe in the prophecy, although Ector and Arthur's best friend, Lancelot, do. When Sir Gareth, the son of Loth, fails to pull the sword from the stone he angrily sparks a battle with the other knights. Arthur, wishing to assist, climbs the stone and, to everyone's shock, frees Excalibur from the stone. The battle stops and the people fall to their knees and praise Arthur as the true king of England. Arthur, frightened, insists that he is a simple squire and not a king. Merlin suddenly appears and reveals Arthur's true heritage. When Ector confirms that he is not Arthur's real father, a shocked Arthur runs away into a nearby forest.