Domnall had been benefactor to St. Mary’s Abbey in Dublin and to the church at Clondalkin. By the end of the 1160’s, he was married to Derb-Forgaill, daughter of Diarmuid Mac Murchada, leader of the rival Ui Cheinnselaig clan. Diarmuid was utterly ruthless, and had previously blinded Muirchertach Mac Gilla Mo-Cholmoc. Diarmuid was now again involved in bitter tribal feuding, and asked the Normans, in 1169, to come across and help him. As part of the deal, Strongbow, leader of the Normans, was offered Diarmuid’s daughter’s hand in marriage. The marriage of Strongbow and Aoife (Domnall’s sister-in-law), amid widespread death and destruction, is one of the iconic scenes from Irish history.
Smal, Chris (1993) Ancient Rathdown and St. Crispin’s Cell, A uniquely historic landscape. Friends of Historic Rathdown, Greystones.