This is an anglicized form of the Olde Gaelic name O Cathail. The Gaelic prefix 'O' indicates 'male descendant of' plus the personal name Cathal, a compound of the Celtic elements 'catu-valus' meaning 'battle powerful'. In Ireland, the name is first recorded in the early half of the 10th century (see below). The principal sept of the O'Cahills belonged to Co. Galway but by the early 13th century their place had been taken by the O' Shaughnessys. Today the name is chiefly found in the Munster counties of Clare, Tipperary, Cork and Kerry. Three townlands called Ballycahill exist in Co. Tipperary. The first element comes from 'baile', a town. Father Daniel Cahill (1796-1864), was a schoolmaster and newspaper editor. He lectured extensively in the United States. The first recorded spelling of the family name is shown to be that of Flan O' Cahill, martyred. which was dated 938 Ancient Irish Records. during the reign of Siol Chuinn, descendants of Conn of the Hundred Battles. 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.