This notable and long-established surname, now widespread in the Irish provinces of Munster and Leinster, is ultimately believed to be of Old Welsh origin, introduced into Ireland in the wake of the Anglo-Norman Invasion of 1169 - 1170, led by Strongbow, a Norman living in south Wales. The derivation is from the Old Welsh personal name "Cadwgan", a diminutive of the Celtic element reflected in the Welsh "cad", battle, or else it is a pet form of "Cadmael, Cadfael, Cadog", a compound of "cad", battle, and "mael", prince. 13th Century recordings of the personal name from Wales include: Cadugan yloyd, and Cadogan Ringild, entered in "Bonds keeping peace" in the reign of Edward 1 (1272 - 1301). The surname first appears on record in the late 13th Century (below), Cadwgan, prince and ruler of south Wales, who died in the year 1112, is said to be the founder of the Earls Cadogan. William Cadogan (1675 - 1726), created first Earl Cadogan (1718), was born in Dublin. Fr. Woulfe and E. MacLysaght, leading authorities on Irish surnames, suggest that the County Cork family of Cadagan or Cadogan are of native Irish origin, their name being an Anglicized form of "O'Ceadagain", descendant of Ceadagan, a personal byname meaning "one possessing hundreds", from "cead", a hundred. However, "Ceadagain" is also liked to be a Gaelicized variant of the Welsh "Cadwgan". On February 24th 1857, Timothy Cadagan and Catherine Buckley were married at Inchigeelagh Parish Church, County Cork. The first recorded spelling of the family name is shown to be that of Cadivor Cadigan, which was dated 1292, in the "Subsidy Rolls of Monmouthshire", Wales, during the reign of King Edward 1, known as "The Hammer of the Scots", 1272 - 1307. 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.