The great and illustrious family of (O)'Sullivan descend from Eoghan Mor, father of the famous Olioll Olum, third Century King of Munster, who was the progenitor of the great Eoganacht clan. The MacCarthy's, O'Keeffes and O' Callaghans were the other leading families of the Munster Eoghanacht, i.e., descended from the above mentioned Eoghan, but (O)'Sullivan remains the most widespread surname in Munster. The name is an Anglicized form of the Gaelic "O'Suileabhan", the Gaelic prefix "O" indicates "grandson" or "male descendant of", plus the personal byname "Suileabhan", variously interpreted as "hawk-eyed" or "one-eyed". Several members of the clan were lords of the territory near Cahir (County Tipperary), prior to the Anglo-Norman Invasion. From 1200 on, they spread to Counties Cork and Kerry dividing into two main septs: O'Sullivan Mor and O'Sullivan Beare. The senior chieftain of the former sept had his stronghold at Kenmare Bay, County Kerry, and the latter chieftain was lord of Beare and Bantry. Owen Rua O'Suileabhan (1748 - 1784), was a great lyric poet, and Sir Arthur Sullivan (1842 - 1900), of the Gilbert and Sullivan operas, was of Irish descent. The first recorded spelling of the family name is shown to be that of Donal O' Sullivan Beare, which was dated 1560 - 1618, hero of the Siege of Dunboy, recorded in "Records of Dunboy, Bantry Bay", County Cork, during the reign of Queen Elizabeth 1 of England, known as "Good Queen Bess", 1558 - 1603. 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.