The surname McKiernan (Irish: Mág Tighearnán), is of Irish origin and is found predominantly in the county of Cavan where it originated. The Irish name is Mág Tighearnán meaning the Son of Tighearnán and the clan or sept takes its name from one Tighearnán who lived c. 1100 AD. He was descended from the 8th-century Dúnchadh, a descendant of Brión mac Echach Muigmedóin. Dúnchadh gave his name to Teallach Dúnchadha (Irish meaning the Hearth of Dúnchadh), the modern day barony of Tullyhunco in County Cavan. Dúnchadh’s brother was Eochaidh from whom the neighbouring McGovern clan of Tullyhaw barony descend.