Nally is the eldest son and one of six brothers, of a prosperous farmer of “advanced nationalist” views. From an early age he is a Fenian, and by the late 1870s is a leading organiser of the Irish Republican Brotherhood.
Nally is also present at the founding meeting in August 1879, of the Land League of Mayo, later becoming the Irish National Land League. He is elected a joint secretary. By 1880, he has become a member of the IRB’s Supreme Council.
In 1879, Michael Cusack, credited with founding the Gaelic Athletic Association, meets Nally, who had in 1877 attempted to start a nationalist athletics association but it never got off the ground. Cusack finds that Nally’s views on the influence of British landlordism on Irish athletics are the same as his.
Cusack recalls how both Nally and himself while walking through the Phoenix Park in Dublin and seeing only a handful of people playing sports in the park so depressed them that they agree it is time to “make an effort to preserve the physical strength of our race.” Nally organises a National Athletics Sports meeting in County Mayo in September 1879 which is a success, with Cusack organising a similar event which is open to ‘artisans’ in Dublin the following April.
In 1881, Nally is sentenced to ten years imprisonment in Mountjoy Prison, Dublin, for what becomes known as the “Crossmolina Conspiracy,” where he is reportedly subjected to harsh treatment. He dies in prison on November 8, 1891. His funeral is organised by James Boland, with whom he had conspired in Manchester.
The resultant Nally GAA Club in Dublin would be closely associated with working class nationalists and republicans during the 1890s and beyond. One of the stands in Croke Park is named after Nally, and is unique for being the only stand in the stadium named after a person who had no connection to the Gaelic Athletic Association.