(King). A prose romance, printed at Paris in 1528, and said to have been discovered in a cabinet hid in the massive wall of an ancient tower on the banks of the Humber, named Burtimer, from a king of that name who built it. The MS was said to be in Greek, and was translated through the Latin into French.
It is also used for Perceval, an Arthurian knight, in many of the ancient romances.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894