Original sentence: He was well-known in Ireland from his youth, as a civil-tongued but adamant advocate of Gaelic culture and history, who had suffered for his adherence to Catholicism, and who was the recognised Ó Conchubhair Donn, profoundly knowledgeable about Irish culture and history
Edited sentence: He was well-known in Ireland from his youth, as a civil-tongued but adamant advocate of Gaelic culture and history, who had suffered for his adherence to Catholicism, and who was the recognised Ó Conchubhair Donn (English: O'Conor Don), profoundly knowledgeable about Irish culture and history