What of Curumo?

[Gwathagor]

I'm pretty sure that Radagast hangs around for a couple millenia. He later assists a young Briton named Arthur in becoming High King of Britain, and is immortalized in medieval legend and romance as the wizard Merlin.

[Ibrîniðilpathânezel]

Originally Posted by Gwathagor

I'm pretty sure that Radagast hangs around for a couple millenia. He later assists a young Briton named Arthur in becoming High King of Britain, and is immortalized in medieval legend and romance as the wizard Merlin.

Ha! I made that same tongue-in-cheek speculation a few years ago. It seems only too appropriate a future for Aiwendil, especially since Merlin was "spirited away" by Nimue. Which one of the Maia ladies came to fetch him, I wonder...?

[Gwathagor]

AND a merlin is a kind of hawk...what more appropriate name for Aiwendil, the lover of birds and beasts, to assume?

[The Might]

A very, very interesting theory.

I was curious to learn more so I of course did what all others do - Wikipedia.
But listen to this interesting part:

In this narrative, Kentigern meets in a deserted place with the naked, hairy madman Lailoken, also called Merlynum or "Merlin", who declares that he has been condemned for his sins to wander in the company of beasts.

Also:

C. S. Lewis used the figure of Merlin Ambrosius in his 1946 novel That Hideous Strength, the third book in the Space Trilogy. In it, Merlin has supposedly lain asleep for centuries to be awakened for the battle against the materialistic agents of the devil, able to consort with the angelic powers because he came from a time when sorcery was not yet a corrupt art. Lewis's character of Ransom has apparently inherited the title of Pendragon from the Arthurian tradition. Merlin also mentions "Numinor," a nod to J. R. R. Tolkien's Númenor.

Who knows if the Professor wasn't somehow influenced by this and was inspired a bit when he created Radagast.

Just a theory, but a good one I think.

[William Cloud Hicklin]

Who knows if the Professor wasn't somehow influenced by this [That Hideous Strength] and was inspired a bit when he created Radagast.

Not possible, since Radagast's creation predated THS by several years. Indeed he goes back at least in name to The Hobbit; and the passages in LR where he is mentioned date from 1939-40.

[The Might]

Indeed something I overlooked.

EDIT: But, he still might have been influenced by the myth.