This surname is of Irish origin, and is an Anglicized form of the Old Gaelic "O'Ciaragain", descendant of Ciarogan, a personal byname from a double diminutive of "ciar", black, dark. Traditionally, Irish family names are taken from the heads of tribes, revered elders, or some illustrious warrior, and are usually prefixed by "Mac", son of, or "O", denoting "grandson, male descendant of". The (O)Kerrigan sept belonged to the ancient population group of Hy Fiachrach, and were located in the Connacht ounties of Mayo, Sligo and Roscommon. A townland called Ballykerrigan, situated in the parish of Balla, County Mayo, specifically locates the sept. At an early date, a branch of this family migrated northwards to County Donegal, and the townland of Ballykergan, in the parish of Kilteevogue near Stranorlar, in County Donegal, is named after this branch. A considerable number of people bearing the name Kerrigan travelled south east to County Armagh, and the name was well established in this county by the end of the 17th Century. On May 1st 1826, Mary Ellen Kerrigan and Thomas Shaw were married at St. Nicholas, Liverpool, Lancashire. John Kerrigan, aged 20 yrs., a famine emigrant to New York, embarked from Dublin on the ship "Wave" bound for that port on May 11th 1846. He was among twenty-one others of the name known to have arrived at New York port during the years 1846 to 1851. The first recorded spelling of the family name is shown to be that of John Kerregen, which was dated April 29th 1695, marriage to Katheren Shepperd, at St. John the Evangelist, Dublin, during the reign of William and Mary, 1689 - 1702. 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.