Recorded in several spellings as shown below this is an Irish surname. It is the developed form of the pre 10th century O' hAileagain, meaning a descendant of 'Aille', which literally means beautiful, but as we are probably talking about the first chief or leader who was probably a soldier or warrior, it may have had a wholly different meaning. They clan originate for the counties Louth and Armagh, and it is said was found there as early as the year 1042. The spellings of the surname are believed to include O' Hallagan, O' Hollegan and Hallegan, in North Connacht, and as Halahan, Hallahan, Hallegan, and even Olligan in County Kildare. Amongst the sample recordings in Ireland is the christening of Margarett Halligan, the daughter of Turlagh Halligan, on February 14th 1655 at Derry Cathedral, Templemore, Londonderry, and the birth of James Halligan on May 24th 1864 at Monasterboice, County Louth. The first recorded spelling of the family name is shown to be that of William O' Halegan, which was dated 1597, in County Kildare, 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.