This notable Irish surname is an Anglicized form of the Old Gaelic "O'Maolagain", descendant of Maolagan, a personal byname from a double diminutive of "maol", bald, tonsured. 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'Maolagain sept is of distinguished origin, its chiefs being lords of a territory called Tir MacCarthain (in the baronies of Boylagh and Raphoe, County Donegal). They also held sway in the adjacent counties of Fermanagh and Monaghan up to the mid 17th Century, when they were largely dispossessed in the Plantation of Ulster. By 1659, the family had migrated southwards, and were found in considerable numbers in the Longford-Westmeath area. Notable bearers of the name were Charles J. Mulligan (1866 - 1916), who was born in County Tyrone, and Rev. William Mulligan (died 1883), professor of Mathematics at Queen's College, Belfast. Hercules Mulligan, confidential correspondent to George Washington, was born at Coleraine in 1740, and died in New York in 1825. During the years 1846 to 1851, one hundred and fifteen persons bearing the name Mulligan are listed on records of Irish famine immigrants who arrived at the port of New York. The first recorded spelling of the family name is shown to be that of John O'Mulligan, Bishop of Leighlin, which was dated 1431, in "Ecclesiastical Records of Leighlin", County Carlow, during the reign of King Henry V1 of England, known as "The Founder of Eton", 1422 - 1461. 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.