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Professor Thadeus O’Mahony (1822-1903), Ballineen, West Cork, Church of Ireland Minister, Professor of Irish at Trinity College Dublin (1861-79), Botanist and the Brehon Law Commission in the 1850s with Dr. John O’Donovan. His father was Cornelius O’Mahony Gentleman. He married Annabella Geoghegan of Rathmines, daughter of Henry in 1856. The same year he was Treasurer of the Ossianic Society in TCD and the O’Donovan Rossa/James Stephens Connection.

He was elected to the Kilkenny Historical Society in 1854 on the recommendation of R. Hitchcock Esq., being at that time Professor of Irish at St. Colomba’s College, Rathfarnham.

The Royal Irish Academy has a collection Graves of the papers between Doctor John O’Donovan and Rev Thadeus O’Mahony re the Brehon Law Commission. The eventual editions are now not hugely well regarded but were most important for the commencement os serious study into the topic. There is a Rev. Thadeus O’Mahony prize in TCD.

O’Donovan Rossa refers to his brother:

James O’Mahony of Bandon wrote to me that he wished to meet me to have a talk over Irish national affairs. He suggested that St. John’s Eve in Ross would be a good place, as crowds of people would be there, and we would escape any prying notice. We met there that day. We had our talk, and then we walked toward the Abbey field. The blind and the halt and the lame were there, in every path and passage way, appealing for alms — appealing mostly in the Irish language. We stood behind one man who was sitting down, his bare ulcerated legs stretched out from him. His voice was strong, and his language was beautiful.

O’Mahony said he never heard or read anything in the Irish language so beautiful. Taking his notebook and pencil to note down the words of the appeal, some traveling companion of the cripple’s told him that a man was taking notes, and the cripple turned round and told us to go away. He wouldn’t speak any more until we went away.

This James O’Mahony was a draper in Bandon ; he was the brother of Thaddeus O’Mahony who was a professor of the Irish language in Trinity College, Dublin. He went to Australia in the year 1863. I hope he is alive and happy there. With him went another comrade of mine, William O’Carroll, who kept a bakery in North Main Street, Cork. They were among the first men in the South of Ireland that joined the Stephens’ movement. It was James O’Mahony that first gave James Stephens the name of Seabhac ; shonk; hawk. The Shouk shoolach — the walking hawk — was a name given in olden days to a banned wanderer. Stephens, at the start of this organization, traveled much of Ireland on foot. A night he stopped at my house in Skibbereen, I saw the soles of his feet red with blisters.

This is a long leap I have taken in the chapter of “from the cradle to the weaning ” — a leap from 1831 — the year I was born — to 1858, the year I first met James Stephens. So I will have to leap back now, and talk on from my childhood……….


Click to access MASTER-Graves-Collection-Catalogue-29-June-2011.pdf

Irish and Celtic languages
This prize was founded in 1931 by a bequest from Miss E.S. O’Mahony in memory of Thaddeus O’Mahony, Professor of Irish 1861-79. It is awarded annually on the results of the Trinity Junior Freshman honor examination in Irish. It must be expended on the purchase of Irish books under the supervision of the Professor of Irish. Value, €450.

Canon Goodman of Skibbereen was also Professor of Irish at Trinity in the 19th century.


Charles Haughey, as Minister for Justice and parliamentary Secretary and the Brehon Laws and the Succession Act.


REv. Thadeus O’Mahony, TCD Professor:

Re Peadar Ó hAnnracháin. Peadar was a wonderful Conradh na Gaeilge organiser throughout a number of counties including Cork and he wrote several books as Gaeilge. He also wrote on the Southern Star as ‘Cois Life’ in the 1940s and 1950s. In that period he worked in the Pigs and Bacon Commission in Dublin.  The column often wandered over long lost history, family relationships and there was a touch of the ‘Seanachaí’ about them.  The daughter of the Gaelic Scholar, landowner and businessman in Ballydehob Thomas Swanton, Crianlarich, gave him her father’s papers.

One of 13 children, 10 of whom survived and the majority emigrated.

In Colaiste Chairbhe (owned by Judge Devoy, New York, later Tony O’Reilly, former CEO, Heinz Corporation).

O’Mahony Family Genealogy:

Courtesy Coppeen, Glimpse of The Past 2017: