Dictionary of National Biography, 1885-1900/Cearbhall
CEARBHALL, lord of Ossory (d. 888), son of Dunghal, was one of the most famous chiefs of the Gall Gaedhel, as the Irish chroniclers call those native tribes who lived in alliance with the Danes. He is called by the Danish writers Kiarvalr, and first appears in history as slaughtering the Danes of Dublin in 845. Six years later he slew the king of South Leinster, and in this war had Danes for his allies. Several of his clan intermarried with the foreigners, and the alliance continued. In 856 they together plundered part of the present Tipperary, and in 857 marched into Meath. Here, however, they made peace with the king of Ireland in the presence of the archbishop of Armagh and the abbot of Clonard. In 858 Cearbhall fought and defeated the Danes of Waterford, and in 859 he joined the king of Ireland in Meath and fought against an invading army of northern Irish. In 861 he defeated the Danes at Feartagh in Kilkenny, and in 862 he plundered Leinster. In 868 the Danes attacked his earthen dun, but were driven off with heavy loss, and Cearbhall was sufficiently secure afterwards to go a foray into Waterford. The next year he crossed the Shannon, and drove off the cattle of both Connaught and Munster, and two years later made a second raid into Connaught. Ossory, his home, being nearly in the centre of Ireland, afforded a good base for operations in any direction, and in 872 he again ravaged the part of Waterford now called Decies. In 875 he was chosen king of Dublin by his Danish kinsmen, and in 876 he gained a victory over the Munstermen near Clonmel. After all these battles he died peaceably in 888. His most constant allies were the Danes of Dublin, but he was ready to join almost any tribe against any other where there was hope of spoil, and was an Irish copy of a Scandinavian rover.
[Annala Rioghachta Eireann, vol. i.; O'Donovan's Tribes and Territories of Ancient Ossory, 1851; Cogadh Gaedhil re Gallaibh, Rolls Series.]