The galloglass families appear to be of mixed Scandinavian and Gaelic Scottish descent. While the medieval Irish genealogists appear to have forged pedigress for the McSweeneys and McDonnells, linking them to the O'Neills of Tyrone and a native McDonnell family from Fermanagh respectively, one galloglass family, the McCabes, were given a much more realistic genealogy. The McCabes were said to have been descended from King Sitric Silkenbeard, the Hiberno-Norse king of the city of Dublin, who gathered the great Viking army in 1014 to fight King Brian Boru at Clontarf. While this genealogy may also be a forgery it is at least a plausible one as King Sitric's descendants fled to the Hebrides after the Anglo-Normans conquered the city of Dublin from the Hiberno-Norse in 1170.
The McCabe mercenaries settled in Ireland at the same time as the McSweeneys and McDonnells (around the late thirteenth and throughout the fourteenth centuries), and took service in Breifne, Fermanagh and Oriel, where they served the O'Rourke, O'Reilly, Maguire and McMahon chieftains. By the mid fiftennth century the head of the family was known as 'constable of the two Breifnes, of Oriel, and Fermanagh', and by the fifteenth and early sixteenth centuries the family was recorded in the Gaelic Irish Annals just like any other local family.
In the year 1602 the Annals of the Four Masters record that the McCabes took part in what was probably the last battle fought between forces of opposing galloglasses in Ireland. In that year the Donegal galloglass chieftain, Donough McSweeney Banagh, an adherent of Red Hugh O'Donnell, surrendered to the English and joined Red Hugh's rival and ally of the English, Niall Garbh O'Donnell. Niall Garbh led his own forces, accompanied by Donough McSweeney and the McSweeneys of Banagh, on a raid into Fermanagh. Once in Fermanagh they were attacked by 'a party of the Maguires and McCabes, in which many were slain'. The important McCabe noble, Brian son of Dugal McCabe was captured in the engagement.
'Brian mc Dubhaill mc a Dubhaltaigh mac Duibh Dáira mc an Ghiolla dhuibh mc Alusdrainn mc Iomarleith mc Néill mhóir mc Somhairle na Madhmann mic Murchadh mhir mc Éogain féil mc Manchaigh mc Giolla Chríosd', who appears to have been an important McCabe chieftain and common ancestor figure, whose genealogy is taken right back to Sitric Silkenbeard and for a further twenty generations to their original ancestor figure.
The McSweeneys and the McDonnells and perhaps the McSheehys of Munster, constables to the earls of Desmond are the most referred to galloglass dynasties when the history of the Ireland of the time is written. However, the McCabes are an interesting family with a rich history and are also very worthy of study.