The wizard named Merlin goes back a long, long way in storytelling – many centuries. [From Wikipedia] The figure known as Merlin is best known from Arthurian* legend. The standard depiction of the character first appeared in Geoffrey of Monmouth’s Historia Regum Britanniae, written circa 1136.
*King Arthur is a legendary British leader of the late 5th and early 6th centuries, who, according to medieval histories and romances, led the defence of Britain against Saxon invaders in the early 6th century.