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 of Saint Wenceslas
Until the 19th century it was believed that the sword was an authentic weapon used by Duke Wenceslas in the 10th century. Later, the sword was considered to be Gothic, made in the 14th century probably by Charles IV who made the new ceremonial crown, which was also dedicated to the main Czech patron saint, St. Wenceslaus. However, a recent detailed technological examination of the sword confirmed that the sword blade was made in the early Middle Ages (probably in the 10th century) and the sword thus really could have belonged to St. Wenceslas. The cross on the blade was probably made later in the Middle Ages and the guard and pommel were added perhaps in the 13th century. In the treasure of St. Vitus Cathedral there are preserved also a helmet and mail shirt, which most likely are Wenceslas’ original armor as well.