In the Elizabethan play The Birth of Merlin, a Saxon magician who served King Vortigern. On his advice, Vortigern sought a young Merlin in order to slake the foundation of a castle with the child’s blood.
Layamon calls this character Joram.
Source
The Birth of Merlin, or the Childe Hath Found His Father | Attributed to William Shakespeare and William Rowley, 1662