McDermott ~ Mac Diarmada

The Story of the McDermott Name

McDermott is the anglicized form of the Irish Mac Diarmada, meaning “son of Diarmaid.” The personal name Diarmaid is ancient in Irish tradition and is traditionally associated with the idea of a “free man.” The Mac Diarmadas became one of the great Gaelic families of County Roscommon, where they ruled as kings of Moylurg for centuries.

The MacDermotts were the hereditary Kings of Moylurg, an ancient kingdom in what is now County Roscommon. Their territory centered around the northern part of the county and extended toward the shores of Lough Key. The family traced its lineage to Tadhg Mac Diarmada, and its chiefs maintained their position in Connacht through the medieval period.

The family's principal stronghold became McDermott's Rock on Lough Key, one of the most evocative sites associated with an Irish surname. The castle and rocky island became a symbol of the family's authority and remain closely connected with the McDermott name today.

The MacDermotts were also closely connected with the powerful O'Connor kings of Connacht. As English influence expanded into the region, the family's political authority gradually declined, although members of the dynasty continued to hold lands and maintain their identity. The surname developed into forms including McDermott, MacDermott, Dermott, and Dermod.

Behind the familiar name McDermott lies the story of a royal Gaelic dynasty of Connacht. From the shores of Lough Key and the ancient kingdom of Moylurg, Mac Diarmada became McDermott, carrying forward the memory of a family that ruled its own Gaelic kingdom for generations and whose ancestral landscape remains one of the most recognizable in Ireland.