Deasy tells Stephen, "I saw three generations since O'Connell's time," implying some claim to historical authority and also perhaps wrapping himself in a bit of the cloak of the great Irish leader. But Deasy believes in very different things than O'Connell stood for, among them Union and anti-Semitism.
Daniel O'Connell (1775-1847), a pioneer of nonviolent resistance to British rule known as The Liberator or The Emancipator, campaigned in the 1810s and 20s for the right of Irish Catholics to become Members of the British Parliament in Westminster (achieved in 1829), and in the 1840s for repeal of the Act of Union, replacing the United Kingdom of Great Britain and Ireland with two nations under one British monarch (never achieved).
In his campaign to restore the Irish Parliament in Dublin, O'Connell staged a series of immense outdoor "monster meetings" in historic Irish locations. Stephen thinks in Aeolus of the two biggest ones: "Hosts at Mullaghmast and Tara of the kings. Miles of ears of porches. The tribune's words, howled and scattered to the four winds. A people sheltered within his voice." Gifford notes that even by the conservative estimate of the British authorities, the August 1843 rally held at the Hill of Tara (northwest of Dublin, the purported seat of Ireland's ancient High Kings) drew 250,000 people.
After the October 1843 rally at Mullaghmast (SW of Dublin, site of a perfidious English massacre in 1577), the British Prime Minister banned another one planned for Clontarf (just north of Dublin, site of High King Brian Boru's decisive defeat of the Vikings in 1014). O'Connell complied with the order to avoid bloodshed, and for his pains was subsequently arrested and sentenced to a year's imprisonment. No more monster meetings were held, and although O'Connell's sentence was shortened, his poor health after his release from prison ended his political campaigns.
In 1847, after making a pilgrimage to Rome, O'Connell died in Genoa. His heart was removed from the body and interred in Sant'Agata dei Goti, the chapel of the Irish College in Rome, a fact noted by Mr. Power in Hades: "He's at rest, he said, in the middle of his people, old Dan O'. But his heart is buried in Rome."
Leopold Bloom thinks in Hades about the "generations" since O'Connell in a vividly personal sense. Standing in the cemetery with the caretaker, John O'Connell, he thinks that "Daniel O'Connell must be a descendant I suppose who is this used to say he was a queer breedy man great catholic all the same." Gifford observes that this thought alludes to "the rumors still persistent in Dublin that Daniel O'Connell had a number of illegitimate children and was thus literally as well as figuratively 'the father of his country.'"
It is not certain that Joyce knew that O'Connell worked to secure the civil rights of Jews as well as Catholics, but O'Connell said to the Jews of Ireland (like Mr. Deasy at the end of Nestor, but sympathetically) that "Ireland has claims on your ancient race, it is the only country that I know of unsullied by any one act of persecution of the Jews." (See http://www.jewishireland.org/irish-jewish-history/history.) O'Connell worked successfully to repeal the ancient English law that prescribed distinctive dress for Jews. His efforts to repeal the Oath of Supremacy that made it impossible for Catholics to become MPs (since it required officeholders to swear allegiance to the King as head of the Church of England) resulted, in 1858, in Parliament creating an exception to the Oath of Allegiance that barred the door to Jews (since it contained the clause, "I make this declaration upon the true Faith of a Christian").
It is tempting to hear an oblique allusion to O'Connell's common cause with Jews in Mr. Deasy's statement that Ireland "has the honour of being the only country which never persecuted the Jews," particularly since Leopold Bloom so strongly shares O'Connell's faith in nonviolent resistance and social reform through legal means. If Joyce intended an allusion to O'Connell in Deasy's bigoted statement, it would highlight Deasy's role as a false father figure to Stephen, connected very indirectly to Bloom by their differing reflections of the great Irish Liberator.