This interesting and unusual name now chiefly associated with the Irish province of Munster, is believed to have originated with the O Dahill sept of Silmurray, County Roscommon, who migrated to Munster prior to the 16th Century. The Gaelic prefix "O" indicates "grandson" or "male descendant of", plus the tribal name "Dahill" believed to derive from the Gaelic "deighil", singular or separate. One, Walter O'Daal "charged with many thefts", who was delivered to Philip de Rupe at Cork gaol in 1295, is considered by some to be the first recorded namebearer, however, this is disputed, and Knogher O'Deaghill, (born 1529), and appointed to determine the bonds of The Earl of Ormond's ancient estates in 1590, is the more likely earliest known holder of the surname. On September 17th 1843, Ellen, daughter of William Dahill and Mary Connor, was christened in Boherbue, County Cork, and on May 14th 1864, John, a son, was born to Michael Dahill and Mary Hennessey in Charleville, County Limerick. The first recorded spelling of the family name is shown to be that of John Roe MacDonagh O'Dahill, which was dated 1579, Records of Bruce, County Limerick, during the reign of Queen Elizabeth 1, "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.