In Ireland, a man enjoyed his status, rights and privileges in virtue of his descent so that genealogical material was of high political consequence.
The O'Kellys of Uí Máine acquired much of their power and wealth in the 14th century and to their credit, many aspect of Gaelic learning such as genealogy, grammar, poetry, sagas, history and folklore thrived under their patronage.
To Murtoogh O'Kelly, bishop of Clonfert and later archbishop of Tuam must go the credit of having produced the great genealogical study known as the Book of Uí Máine.
So also John Lynch, another noted Galway 17th century scholar who wrote in both Gaelic and Latin, refers to it in his book "Cambronais Eversus" as "Liber Odubhegan and quotes from it on at least six occasions.
The Sligo-born Dubhaltach Mac Firbhisigh, a contemporary of O'Flaherty and Lynch, used "Leabhar Ó Dubhagáin" as a source of material for his "Seancahs Síl Ir".
John O'Donovan in his book The Tribes and Customs of Hy Many refers to the old manuscripts of Teige O'Dugan, "an eminent historian of about 90 years ago".
Murchadh Riabhach O'Cuindlis, the scribe who compiled the massive text of the Leabhar breac (1408–11) and who was a native of Ballydacker near Athleague was more than likely of the same stock as the O'Dugans.
According to Simmington's "Transplantations to Connacht", they lost their lands during the Cromwellian confiscations but in 1658, the commissioners in Loughrea regranted 75 acres to Teigh O'Doogane in the parish of Ahascragh.
Griffith's Valuation shows John O'Doogan in possession of 74 acres 1 rood and 15 perches in the townland of Killasolan, parish of Ahascragh.
In a by-election which was called for the county in 1872, Dr. Duggan, now Bishop of Clonfert, organised support for Captain J.P. Nolan who was favourably disposed towards tenants rights.
Nolan was elected but lost his seat on the grounds of undue clerical influence and Dr. Duggan was brought to trial with others before the Court of Common Pleas, but the case collapsed and he was acquitted.
In the north, Dugan, Dougan, and Doogan are common, a large portion descended from families originally in County Fermanagh.
Throughout other English speaking countries, Dugan and its many variants, including Duggan, Dougan, Doughan, Doogan, and Duggin are widespread.