According to the Lebor Gabála Érenn he was chosen as king by the remaining quarter of the men of Ireland after the other three-quarters had died with the former king, Tigernmas, while worshipping the deity Crom Cruach.
He introduced a system whereby the number of colours a man could wear in his clothes depended on his social rank, from one colour for a slave to seven for a king or queen.
He ruled for four years, until he was killed in battle at Tara by Cermna Finn, who succeeded to the throne jointly with his brother Sobairce.
[18] The chronology of Geoffrey Keating's Foras Feasa ar Éirinn dates his reign to 1159–1155 BC,[19] that of the Annals of the Four Masters (which adds that there was a seven-year interregnum between Tigernmas' death and Eochaid's accession) to 1537–1533 BC.
His father, Daire Doimthech, should not be confused with another different person, also called Dáire Doimthech, who was a son of Sithbolg, and was a legendary King of Tara.