One of the seven signatories of the Proclamation in 1916, he was born in Cloughjordan in 1878, son of teachers Joseph MacDonagh and Mary Louise Parker. He had two sisters and three brothers. He went to Rockwell College, Cashel, Co Tipperary in 1894 initially to train as a priest but found he did not have a vocation and became a teacher. He taught in St Kieran’s College Kilkenny (1901-1903) and in St Colman’s College in Fermoy, Co. Cork (1903-1908) before joining the staff at St. Enda’s School in Dublin in 1908. He was a member of the Gaelic League.