Like most of their neighbours, the family were tenant farmers "who lived in a three-roomed house and raised grains, root crops and livestock for sale at local markets.
He was certified to teach Irish in national schools in 1907 and two years later became the full-time múinteoir taistil (travelling teacher) for the Gort area.
His participation in the Easter Rebellion of 1916 was cut short by his arrest at Kinvara presbytery, while the main group of over six hundred Galway volunteers gathered near Athenry and Oranmore under Liam Mellows and Larry Lardner.
Following the death of the latter, his wife and two fellow officers at the Ballyturin ambush, Ó Fathaigh's family home was burned by Crown forces, after which they ran riot in Gort.
In later years he worked as a Health Board clerk for Galway County Council and was secretary of the committee which erected a monument to Liam Mellows in Eyre Square.