This is an Anglicized form of the Old Gaelic name Mac Mathghamhna. The Gaelic prefix "mac" means "son (of)" plus the personal byname Mathghamhan, a bear. Mathghamhan was the son of Cian MacMael Muda, a 10th Century Prince and his wife, Sadbh, who was the High King, Brian Boru's daughter. In modern Gaelic the name is written as O' Mahuna and Anglicized as (O) Mahony and (O) Mahoney. The sept belonged almost exclusively to south west Munster where they built fourteen fortified castles including one at Rosbrin in Co. Cork. The famous "Bells of Shandon", a poem about Cork City, was written by Sylvester Mahony under the pseudonym Father Prout. John O' Mahony (1816 - 1877) was co-founder of the Fenian Brotherhood (1858). He translated Keating's Gaelic "History of Ireland". The first recorded spelling of the family name is shown to be that of Father Francis O' Mahony, which was dated 1626, Provincial of the Irish Franciscans, during the reign of King Charles 1, "The Martyr", 1625 - 1649. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.