The Clan/Sept History

Ossory an ancient kingdom of Ireland that won for itself a semi-independent position as a state within the kingdom of Leinster, probably in the 1st century AD. In the 9th century it was ruled by an able king, Cerball, who allied himself with the Norse invaders and figured in later centuries as an ancestor of some important families in Iceland. When surnames were introduced, the dynasts descended from him in Ireland were known as Mac Gillápadraig, a name transformed under Norman influence into Fitzpatrick. In the 11th century they contended for the kingship of Leinster but were soon overwhelmed by the south Leinster family of MacMurrough.
Legend records that the Fitzpatrick clan descended from Milesius, King of Spain. Milesius planned to go to Ireland, but died before he could make it. Scota, wife of Milesius, and their three sons did make it Ireland. Eireamhon, son of Miesius and Scota, is thought to be the ancestor for the Fitzpatrick family.