The Dal gCais were the great clan of
Thomond, or North Munster, an area more especially associated with
County Clare (excluding the Burren and Corcomroe on the northwest
corner) and adjacent parts of Tipperary and Limerick. They were the
axe-wielding footsoldiers who formed the core of the army that
defeated the Vikings in 1014, one of the most significant dates in
Gaelic history. The chief families of this tribe were above all the
O’Briens, but also O’Ahernes.