"When Ireland was founded by the Mac's and the O's, I never could learn..." but the singer lists all the various great family names of Ireland. Some specific names are mentioned, but most are simply references to clans
Even when a specific character is named in this song, it is often a legendary figure such as Finn MacCool. A handful, however, are historical, such as Hugh O'Neill of Tyrone, whose name is naturally connected with O'Donnell (for these two, see the notes to "O'Donell Abou").
The final stanza refers to women, and most of these, interestingly, are women of song, e.g. Eileen Aroon and Kathleen Mavourneen. - RBW