From: Early Irish History and Antiquities and the History of West Cork
By Rev. W. O’Halloran
1916

The O’Mahonys of West Cork

Dr. Smith says: ” These Mahowns derive their pedigree from Kean Mac Moyle More, who married Sarah, daughter to Brian Boru, by whom he had Mahown, the ancestor of all the sept. It is from this Kean the village of Iniskeen, in Carbery, has its name, and from this sept that Bandon is sometimes called Droghid Mahon. Mahon was the ancestor of the Mahonys, or O’Mahonys.”
The O’Mahonys, whose stronghold was in the neighbourhood of Bandon (Drohid Mahon), were the first to encroach on the territory of the O’Driscolls. This occurred long before the Anglo-Norman invasion. They possessed themselves of the western portion of Corca Laidhe called Ivahah, which comprised the parishes of Kilmoe, Schull, Durrus, Kilchrohane, Kilmacougue, and Caheragh. They had fourteen strongly built castles.
The Rosbrin family and the proprietor of Dunbeacon Castle joined the Desmond rebellion in 1579. The head of the O’Mahony sept kept aloof.
Sir Thomas Norreys, Lord President of Munster, spent some time at Ross in 1599 looking out for the arrival of the Spaniards. He writes to the Privy Council on the 26th of March: ” Since my last letter in Ross, I continued in this country until March 16th, but could find no confirmation of the arrival of the Spaniards. I returned home by Kinelmeky, where the O’Mahons dwell, and burned their corn and spoiled the country.” When the corn was young they destroyed it by a specially made harrow called a ” pracas,” and when it was in a more advanced stage by sickles and swords.
The Spanish expedition, as already stated, was supported by the O’Driscolls and O’Sullivan, and likely the head of the O’Mahonys would have joined it only that he was cast into prison at the time by Carew, who invited him ostensibly to the assizes then being held in Cork.
Some of the O’Mahonys migrated into Kerry and settled near Killarney, Castleisland, and Kenmare, and were people of importance, their descendants remaining to the present day. In 1584 commenced the decay of the sept, and the subsequent wars proved disastrous to it