In a Welsh Myrddin poem known as The Prophecy of Myrddin and Gwenddydd, Gwenddydd, Myrddin’s sister, says,
I ask my Llallogan Myrddin, a wise man, a prophet.
Llallogan is general translated as “twin brother”. It is possible Lailoken was merely a nickname for Merlin, as Lailoken resembles the Welsh word for a twin and Merlin was thought to have a twin sister, Ganieda.
Lailoken’s legend is very similar to Myrddin’s: Lailoken was said to have participated in a battle between the towns of Lidel and Carwannock. His side suffered enormous losses, and an apparition in the sky blamed Lailoken for the deaths. This episode parallels Myrddin’s experience at Arfderydd. Lailoken went insane and ran off to live in the forest like a wildman, where he spewed random prophecies of his own “triple” death and of the downfall of Britain.
Lailoken was befriended by Saint Kentigern, who gave Lailoken his Last Rites at Lailoken’s request, even though Lailoken’s prophecy of his own death seemed impossible: he claimed he would die from a beating of sticks and stones, then from being impaled through the heart with a stake, and then from falling into water. Later, as Lailoken was wandering through a field near Dunmeller (Drumelzier), Meldred’s shepherds spied him and stoned him. As he began to perish from the beating, he fell off a cliff into the River Tweed – and was impaled through the heart by a protruding stick.
The Romance of Merlin | Peter H. Goodrich, 1990