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.
Triumph or Agony
"The Myth of the Holy Sword" presents the history of the Emerald Sword in the Emerald Sword Saga. During the third Elvish war in the battle for Galfor's mines, the warrior Naimur was captured by Atlon (referred to as "Hell's Fury"). Atlon tortured Naimur using an emerald stone to drain his energy and eventually killed him. After the battle, Loinir, Naimur's brother, took the stone used to torture Naimur and forged the Emerald Sword. Loinir asked the angels to bless the sword, filling it with their holy might.