<P> Geoffrey's rendering of the character was immediately popular, especially in Wales . Later writers expanded the account to produce a fuller image of the wizard . Merlin's traditional biography casts him as a cambion: born of a mortal woman, sired by an incubus, the non-human from whom he inherits his supernatural powers and abilities . Merlin matures to an ascendant sagehood and engineers the birth of Arthur through magic and intrigue . Later authors have Merlin serve as the king's advisor and mentor to the knights until he is bewitched and imprisoned by the Lady of the Lake . </P> <P> The name "Merlin" is derived from the Welsh Myrddin, the name of the bard Myrddin Wyllt, one of the chief sources for the later legendary figure . Geoffrey of Monmouth Latinised the name to Merlinus in his works . Medievalist Gaston Paris suggests that Geoffrey chose the form Merlinus rather than the regular Merdinus to avoid a resemblance to the Anglo - Norman word merde (from Latin merda) for feces . </P> <P> Clas Myrddin or Merlin's Enclosure is an early name for Great Britain stated in the Third Series of Welsh Triads . Celticist A.O.H. Jarman suggests that the Welsh name Myrddin (Welsh pronunciation: (ˈmərðɪn)) was derived from the toponym Caerfyrddin, the Welsh name for the town known in English as Carmarthen . This contrasts with the popular folk etymology that the town was named for the bard . The name Carmarthen is derived from the town's previous Roman name Moridunum, in turn derived from Celtic Brittonic moridunon, "sea fortress". </P> <P> Geoffrey's composite Merlin is based primarily on Myrddin Wyllt, also called Merlinus Caledonensis, and Aurelius Ambrosius, a mostly fictionalised version of the historical war leader Ambrosius Aurelianus . The former had nothing to do with King Arthur: in British poetry he was a bard driven mad after witnessing the horrors of war, who fled civilization to become a wild man of the wood in the 6th century . Geoffrey had this individual in mind when he wrote his earliest surviving work, the Prophetiae Merlini (Prophecies of Merlin), which he claimed were the actual words of the legendary madman . </P>

What happened to merlin in the arthurian legend