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.
Prince Valiant
When the strip starts in 1937, Val is five years old. The first episodes follow the youth through the wild Fens district of Britain with his father, the deposed King Aguar of Thule. When Val encounters the witch Horrit she predicts he will have a life of adventure, noting that he will soon experience grief. Arriving home, Val discovers that his mother has died. Not long after this come encounters with Gawain, with gigantic creatures and with the glory of Camelot. Steve Donoghue comments:
Val acquires the Singing Sword in strips from 1938. The original owner of the Singing Sword is Prince Arn of Ord, Valiant's rival for the maid Ilene. The two men put aside their differences when Ilene is kidnapped by Viking raiders on her way to Ord. Arn hands Valiant the charmed sword to help him hold back their pursuers while he himself rides ahead to free Ilene. The pair continue in their efforts to rescue Ilene, eventually discovering that she has been killed in a shipwreck. Arn gives the Singing Sword to Valiant after that adventure and the two part as friends. Later in the series it is mentioned that the Singing Sword is a sister to King Arthur's Excalibur.