The 'Book of Leinster' which was written in the 13th century, recounts the story of Amergin who was known as the poet from the river Bush who grew up to become the chief poet to the King of Ulster. It describes him as a warrior poet and chief of his clan. He is described as wearing a blue, fine bordered shirt next to the skin, with carved and interlaced clasps of white bronze, with buttons burnished gold in its opening and breast; above this he wore a coat of the most beautiful colours. He was the son of a master blacksmith named Uel who lived at Ballaghmore beside the river Bush, on the farthest edge of the Kingdom of Dalriada.
Amergin was born dumb and never spoke until he was fourteen years old. On the day he spoke for the first time, Athern, Ulster ’s chief poet, had sent his servant to the blacksmith's to order a new axe to be forged. While he was there, Amergin began to speak but not in a normal way, he spoke very articulate and poetically. The servant listened in total amazement at the flow of words, he had never heard anything like it before not even from his master Athern, he was both shocked and surprised as he knew Amergin was dumb. When the servant on arriving home he told Athern about the miracle that had happened. Althern felt very threatened by this and over a few days he resolved to kill Amergin in fear that he would take his place as the chief poet of Ulster. Amergin’s father also realised this possibility and made a likeness of his son, dressed it in clothes and set it down in the corner of the smithy. When it was time to collect the axe, instead of sending the servant Athern came himself.
He lifted the axe admiring the beauty and craftmanship, at the same time he a noticed the shape of a boy sitting in the corner which he was convinced was Amergin. He took the new axe and swung as if admiring its power and balance, then suddenly he rush over and brought the axet down on the likeness of Amergin and then turned and fled, thinking he had killed him. Amergin’s father also forged swords for the King of Ulster, so the word soon spread to the king about what had happened. When the king heard about this he called for Athern’s to come to see him. As punishment the king ordered Athern to take Amergin as his foster son and teach him all the prose he knew, so Amergin could hone his gift with words.Soon Amergin became the chief of all the poets of Dalriada and afterwards the chief poet to Connor McNeese, the King of Ulster. He married the sister of the King and their son was the Ulster warrior Conall Cernach.