On the death of Carláen, the Bishop of Armagh, on 24 March 588, Eochu was appointed as the 13th coarb in succession to Saint Patrick.
Eochu is referred to as a witness to a contract guaranteeing the rights of the Airgialla clan, as follows- "Who binds the witnesses of the contract, it is not a cause of subjection, Bishop Echu, Bishop Aed mac Bric, Senach son of Máel" [REF].