This surname is of Irish origin, and is an Anglicized form of the Old Gaelic "O'Duibhginn", descendant of Dubhceann, a personal byname from "dubh", black, dark, and "ceann", head. Traditionally, Irish family names are taken from the heads of tribes, revered elders, or some illustrious warrior, and are usually prefixed by "Mac" denoting "son of", or "O", grandson, male descendant of. The O'Duibhginn sept belonged to the barony of Clandonagh in the Leinster county of Laois, and the most notable family of the name, that of Kyle parish in West Laois, were keepers of the Bell of St. Molua. In the process of Anglicization "O'Duibhginn" acquired many variant forms including (O)Deegan, Duigan, Deehan, Dig(g)in and Deighnan. In the Fiants (Fiant litterae patentes), the name appears as O'Doygan and O'Diggen (see below), and in Petty's "Census" of all Ireland, taken over a century later (1659), the spelling Deegan, Duigan and Deighnan are recorded. The last mentioned form is particularly widespread in Ulster where the name is occasionally interpreted as an Anglicization of the Old Gaelic "O'Diochan" or "O'Deaghain", descendant of the Dean. On October 12th 1864, Catherine, daughter of Owen Deighan and Mary Murphy, was christened at Kilmore, County Monaghan, and on February 9th 1865, the birth of James, son of James Deighan and Eliza McPoyle, was registered at Eglinton, Londonderry. The first recorded spelling of the family name is shown to be that of O'Doygan, which was dated 1560, in the "Elizabethan Fiants Records", during the reign of Queen Elizabeth 1, 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.