Ex·cal·i·bur 
(ĕk-skălə-bər)
(ĕk-skălə-bər)n.
In Arthurian legend, the sword belonging to King Arthur.
[Middle English, alteration (perhaps influenced by Latin chalybs, steel) of Medieval Latin Caliburnus, from Middle Welsh Caletuwlch or Middle Irish Caladbolg, a legendary sword.]