Geoghegan

Often spelled without the prefix "Mac", the name has many variants, including Gehegan, Geoghan, Geohegan, Gahagan, Gagan, and Gagon which approximate the most common pronunciations of the name.

Niall's ancestry is claimed by Irish myth to trace back to Miledh of Esbain, King of Spain, whose wife Scota was the daughter of the Egyptian Pharaoh Nectanebo II.

[3] O'Rahilly suggests that the nine hostages were from the kingdom of the Airgialla (literally "hostage-givers"), a satellite state founded by the Ui Néill's conquests in Ulster, noting that the early Irish legal text Lebor na gCeart ("The Book of Rights") says that the only duty of the Airgialla to the King of Ireland was to give him nine hostages.

[4]: 222–232 His son Fiachu mac Néill is said to be the ancestor of the Cenél Fiachach, a clan which included several well known sub-clans or septs such as Geoghegan and O'Higgins, whose lands extended from Birr to Uisnech in southern Westmeath and part of north Offaly and their southern territory became known as Fir Cell (land of the churches), and later the Barony of Moycashel.

This claim so enraged the descendants of Fiachu, that they killed the author of the passage, even though he was under the protection of Suanach, the abbot of the monastery of Rahin.