Recorded in many forms as shown below, this is an Irish surname. It is a development of the Old Gaelic name O' Duibhginn, or literally a male descendant of Dubhceann, this being a personal byname meaning dark headed one. Traditionally Irish family names are taken from the heads of tribes, and were originally prefixed either by Mac or Mc denoting "son of", or O', 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 development O'Duibhginn acquired many spellings including O' Deegan, Deegan, Deegin, Degan, Deehan, Diggin and Deighnan. In the records known as the Fiants, the name also appears as O' Doygan and O' Diggen (see below). Examples of recordings include that on October 12th 1864, of Catherine, the daughter of Owen Deeghan and Mary Murphy, 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 Teag O' Doygan. This was dated 1560, during the reign of Queen Elizabeth 1st of England, 1558 - 1603. Surnames became necessary when governments introduced personal taxation. In England this was sometimes known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.