If you research the O’Neachtain clan and it’s origins then you will quickly find that it is decently documented; there are entries on the O’Neachtain clan in many of the notable early Irish history sources.
Here is a great place to start – Irish Names and Surnames by Rev Patrick Woulfe . In this book we find an entry for ‘O Neachtain’ — this entry will provide us with a great deal of information and other subjects/topics to continue our research.
First, this source lists different formulations of the O’Neachtain surname as: “O Naghtan, O Neaghten, O’Naughton, Naghten, Naghton, Naughtan, Naughten, Naughton, Nocton, and Norton”
This source also lists 2 different groups of people under this name:
- A Dalcassian Family, of the same stock as the O’Quinn, numerous in Thomond.
- A branch of the Ui Maine in Galway and Roscommon. This family descends from Fiachrach Fionn, grandson of Maine Mor – the progenitor the Ui Maine.
- Furthermore, this source says that the O’Maolaidhlaidh (O’Mulally) are close kin and formerly both families forming originally under the common designation of ‘Ui Fiachrach Finn’.
- Lastly this source says that the O’Neachtains were chief of the Maonmagh, the plain laying around Loughrea. This lasted until the time of the Norman Invasion. At that time they were ‘removed’ to the Fews (Feadha) of Athlone. This group formed a distinct clan till the time of Elizabeth.
From here we can research more about O Neachtain in other sources, specifically this clan name ‘Ui Fiachrach Finn’ and their place within the Ui Maine.