He acquired a degree in engineering at University College Dublin, where he first became acquainted with Irish speakers from Connemara.
[2] He learned Irish as a second language at school and among native speakers in the Connemara Gaeltacht.
Ó hÉallaithe is known as a Gaeltacht activist and commentator, though he has always acted as an individual rather than on behalf of an organisation.
[3] He first became aware of Irish as a living traditional language when he and others in his school class went with a teacher to Corca Dhuibhne in County Kerry.
[6] Ó hÉallaithe helped publicise the research contained in a report entitled "Comprehensive Linguistic study of the Use of Irish in the Gaeltacht" (2007), a document which showed a steep decline in Irish language use in the Gaeltacht.