The term 'Holy GRAIL' is a reference to the CUP that Jesus Christ used at the Last Supper. It is also known as the GRAIL, and is a symbol of purity and holiness. In Arthurian legend, it is the object of a quest by the Knights of the Round Table. The term 'GRAIL' is derived from the Latin word 'gradalis', which means 'CUP'. The term 'Holy GRAIL' is often used to refer to something that is highly sought after or difficult to obtain.