Myrddin

Myrddin Wyllt is the Welsh legendary character that became Geoffrey Monmouth's Arthurian character Merlin, who may have also been inspired by the legendary Welsh figure Emrys. To be clear, Merlin, Latinized as Merlinus, came after Myrddin. His own tale closely resembled Lailoken, a British figure found in the 12th century Life of Kentigern, but in the 15th century they may have blended a bit. A madman living in the Caledonian forests, he was an ex-bard reflecting over his life, who'd become wild and mad, and may have had some power of prophecy. The name Myrddin derives from the capital of the Demetae tribe called Moridunum, meaning "sea fort." As an important note, the place Caerfyrddin means "Myrddin's castle" and was supposedly his place of birth.

Myrddin can also be found as a Stargate character, and it was the name of Welsh writer Myrddin Fardd.

Mryddin has never shown up in U.S. data, while Merlin has been used since at least 1885. It started with just 5 boys given the name in 1885 and had a high of 389 in 1927. Now Merlin is down to 54 boys in 2017.