The Irish Ó Dubhagain, from a diminutive of dubh, "black", is anglicised principally as "Duggan", but may also be found as "Dugan" or "Doogan", the latter representing a more accurate rendition of the Irish pronunciation. The surname arose simultaneously in a number of areas, including Cork, Roscommon/Galway, Wexford and Fermanagh. The best known family of the name had their territory near the modern town of Fermoy in north Cork, and were originally the ruling family of the Fir Maighe tribal grouping which gave its name to the town. They claimed descent from Mug Ruith, the legendary magician of the Fir Bolg. They ceded pre-eminence to the O’Keeffes in the eleventh century, but remained powerful in the area. Along with the other Fir Maighe families they lost their power when the Normans conquered the territory in the twelfth and thirteenth centuries. The family name is found in the parish and townland of Caherduggan in that area.
Another sept of the same name is famous in the Uí Maine area of east Galway/south Roscommon principally because it produced John O'Dugan (died 1372), chief poet of the O'Kellys, and co-author of the "Topographical Poems", a long, detailed description of Ireland in the twelfth century.
In Wexford, the original Irish name was Ó Duibhghinn, which is also rendered as Doogan and (closer phonetically to the original) Duffin. The genealogy of the Wexford Duggans became a matter of considerable interest in the early years of this century when the story of the so-called "Duggan Millions" became known. One Alfredo Duggan of Argentina, descendant of a Wexford emigrant, had died an extremely wealthy man, with no heirs. Eventually, in 1944, a nephew then aged 72 and originally from Rosslare, inherited several million pounds.
In the north of Ireland the versions Dougan, Dugan and Doogan are quite common. Many of these are descended from the Ó Dúgáin, originally from Inishkeen in Co. Fermanagh, but Dugan and Dougan are also well-known Scottish names and many in the north will be of this connection. In 1890 Doogan was most common in Antrim, Armagh and Donegal, while Dugan was frequent in Antrim and Down.
The arms of the family appear to derive from a pun on some of the elements of the name dubh meaning "dark", and an meaning "light".
. Patrick Duggan (1813-1896) was of the Galway/Roscommon family. He became Bishop of Clonfert and is best remembered for his part in the election in Galway in 1872, for which he was tried and acquitted.
Augustine Duganne (1823-1884) was a well known American poet and story writer.
Eamonn Duggan (1874-1936) was a nationalist T.D. in 1918, a signatory to the Anglo-Irish Treaty in 1921 and Minister of Home Affairs in the first Free State government.
Noel C. Duggan (1933 - ) is one of Ireland’s best known businessmen. A native of Millstreet Co. Cork, he has built the Green Glens equestrian centre there into an arena capable of hosting the largest international entertainment events, including the Eurovision Song Contest in 1993.