HARD CRACK

Despite Arthurian legend being set in the fifth and sixth centuries, the first use of the name Excalibur in English was in the 1300s, when it was spelled Excalaber. Before that, the Old French words Escalibor and Escaliborc were the standard, and they just added an es sound to the beginnings of the words Calliborc and Calibourne for no reason. Those are from Medieval Latin Caliburnus (which is still only from the twelfth century), which finally derives from Old Welsh Caledfwlch. That, in turn, is composed of the roots caled, meaning "hard", and bwlch, meaning "crack" (the development of calib was due to influence by a Latin word for "steelwork"). Caled traces to Proto-Indo-European kel​, meaning "hard", and bwlch is also PIE through Proto-Celtic. Excalibur is also etymologically related to a legendary Irish sword named Caladbolg, which literally translates to "hard belly"