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.
Sword
Naue II swords were exported from Europe to the Aegean, and as far afield as Ugarit, beginning about 1200 BC, i.e. just a few decades before the final collapse of the palace cultures in the Bronze Age collapse. Naue II swords could be as long as 85 cm, but most specimens fall into the 60 to 70 cm range. Robert Drews linked the Naue Type II Swords, which spread from Southern Europe into the Mediterranean, with the Bronze Age collapse. Naue II swords, along with Nordic full-hilted swords, were made with functionality and aesthetics in mind. The hilts of these swords were beautifully crafted and often contained false rivets in order to make the sword more visually appealing. Swords coming from northern Denmark and northern Germany usually contained three or more fake rivets in the hilt.