- Not to be confused with Loch Doon Castle
The name of the castle in today's Irish is ‘’Caisleán an Dúin’’, tautologically meaning ‘Fort Castle’. The name is from that of an earlier, Gaelic fortress on the site known as Dún Mughdhord.
The Norman Castle of Doon appears to have been built on the site of the old Irish Dún Mughdhord. The castle has almost disappeared. The castle is in the townland of Dooncastle. According to local accounts, the stones of the castle were used by Lord Sligo in the building of Westport House. The castle is on a hill 150 feet in height and gave excellent views to the east and south-east to Islandeady and Aille, where the other McPhilpin castles were. The space on the hill is in the shape of an ellipse 40-60 yards x 20 yards. The castle was rectangular and measured about 40 feet x 27 feet. The space between the main castle and the outer fortifications was not great.
- The history of the County of Mayo to the close of the Sixteenth Century by Hubert Thomas Knox 1908 pg. 45
- Aughagower by John Keville, Cathair na Mart Vol. 3 (Journal of Westport Historical Society)
- The history of the County of Mayo to the close of the Sixteenth Century by Hubert Thomas Knox 1908 pg. 301