Word Origin & History
early 14c., from O.Fr. graal "cup," earlier "flat dish," from M.L. gradalis "a flat dish or shallow vessel," perhaps ult. from L. crater "bowl," from Gk. krater "bowl, especially for mixing wine with water." Holy Grail is M.E. Sangreal (Saint graal), grafted awkwardly onto the Celtic Arthurian legends
12c. by Church scribes in place of some pagan Otherworldly object. It was said to be the cup into which Joseph of Arimathea received the last drops of blood of Christ (according to the writers who picked up the thread of Chrétien de Troyes' "Perceval") or the dish from which Christ ate the Last Supper (Robert de Boron), and was ultimately identified as both (e.g. "þe dische wiþ þe blode," 14c.).