genealogies of the families
(O)DUFFY, Duhig, Dowey The name Duffy or O'Duffy is widepread in Ireland: it is among the fifty commonest surnames; standing first in the list for Co. Monaghan, it is also very numerous in north Connacht. It is found in Munster to some extent but there it often takes the form Duhig, while in parts of Donegal it has become Doohey and Dowey. These variants arose from local pronunciations of the Irish Ó Dubhthaigh, a sumame in which the root word is dubh (black).
There were several distinct septs of O'Duffy. One belongs to the parish of Lower Templecrone in the diocese of Raphoe, Co. Donegal, the patron saint of which is the seventh century Dubhthach, or Duffy. His kinsmen the O'Duffys were erenaghs and coarbs there for eight hundred years. The Connacht sept, the centre of whose territory was Lissonuffy or Lissyduffy near Strokestown, named after them, was remarkable for the number of distinguished ecclesiastics it produced, particularly in the twelfth and thirteenth centuries. Among the many abbots and bishops whose names are recorded in the Annals and in the Rental of Cong Abbey, compiled by Tadhg O'Duffy in 1501, the most noteworthy were Cele (also called CadWa and Catholicus) O'Duffy, Archbishop of Tuam, who was King Roderick O'Connor's ambassador to Henry II in 1175, and Muiredagh O'Duffy (1075-1150), also Archbishop of Tuam. This family was much occupied with ecclesiastical art and was responsible for making the famous Cross of Cong. They are traditionally believed to have originally been located in east Leinster, of the same stock as the O'Byrnes and O'Tooles. The same origin is claimed for the O'Duffys of Monaghan. There, too, they were remarkable for their contribution to the Church; but in this case not for mediaeval dignitaries, but for the extraordinary number of parish clergy of the name: for example, in the lists of priests and sureties compiled for Co. Monaghan in accordance with the Penal Laws in the eighteenth century Duffy is by far the most numerous name. One other priest must be mentioned, though he has no apparent connection with these, since he was vicar of Tubrid in the diocese of Waterford, viz. Father Eugene (or Owen) O'Duffy (c. 1527-1615), a famous preacher who always used the Irish language in his sermons: he was the author of the well-known satire on the apostate bishop Miler Magrath.
In other spheres O'Duffys have distinguished themselves in 'the nineteenth and twentieth centuries. Among these we may mention Edward Duffy (1840-1868), the leading Fenian in Connacht, who died in an English prison; Monaghan born James Duffy (1809-1871), the founder of the well-known Dublin publishing firm; and three members of the Gavan Duffy family (which, by the way, is not a hyphenated name) -- Sir Charles Gavan Duffy (1816-1903), also of a Co. Monaghan family, founder of the Young Ireland party and The Nation newspaper, subsequently Prime Minister of Victoria, Australia; his son John Gavan Duffy (1844-1917), also a member of the Victoria government, though born in Dublin; and of the third generation a very prominent figure in modern Irish politics, George Gavan Duffy (1882-1951), one of the signatories of the Anglo Irish Treaty of 1922 and later President of the High Court of Justice of Ireland.
The variant Duhig occurs in Munster. Sir James Duhig, the late Archbishop of Brisbane, was born at Limerick in 1871. He held that position for 46 years. His predecessor, the first Archbishop, Robert Dunne (1830-1917), a native of Ardfinnan, Co. Tipperary, held it for 30 years. The first bishop was James Quinn, appointed in 1859. He was so successful in promoting Irish emigration to Australia that his critics sarcastically suggested changing the name of Queensland to Quinnsland.
The Mayo surname O'Doithe, formerly anglicized O'Diff, presents an example of the absorption of uncommon names by common ones: the O'Diffs have now become generally Duffys and so are hardly distinguishable from the O'Duffys of the adjoining county of Roscommon.
Source:Irish Families by Edward MacLysaght MA, D Litt, MRIA - Irish Academic Press 1991