The name occurs in only a small number of surviving sources, which for this region of Ireland, of once respectable wealth, are generally quite poor.
According to the early tale known as Conall Corc and the Corcu Luigde, Saint Colmán of Cloyne cursed the city of Ressad, which brought down its walls.
The author of CGG states he was one of the Munster kings slain by Ivar of Limerick circa 967 before the Battle of Sulcoit.
[4] Faelan, son of Cormac, king of the Desi, and Flathri, son of Allamaran, king of Ressad, and Sidechad, son of Segni, king of Titill... were killed by Ivar of Luimnech and the foreigners who were with him, because they were endeavouring to hinder the expedition.Finally, whether related to Ress/Ressad or not, there is also a Flann Ressach in one of the Uí Cairbre (ancestral to O'Donovan and other families) pedigrees preserved in the Book of Glendalough (this particular entry having been copied from the lost Psalter of Cashel).
[5] It is possible that the Ráth called Reerasta, where was found the internationally famous Ardagh Chalice (Hoard) in western County Limerick, is a corruption of Rí Ressad.