Mac Aodhagáin was the name of an Irish family of Brehons who were hereditary lawyers - firstly to the Ó Conchobhair Kings of Connacht, and later to the Burkes of Clanricarde.

The earliest surviving Irish law manuscript, In Senchas Már, was written prior to 1350 at a school (patronised by the Mac Aodhagáin) at Duniry, near Loughrea. Other branches of the clann maintained schools at Park, outside Tuam, and at Ballymacegan in Co. Tipperary. The work known as Leabhar Breac was produced by one of their students, while Dubhaltach MacFhirbhisigh may have studied at Ballymacegan under Flann Mac Aodhagáin up to the year 1643.^{[citation needed]}

The surname is now rendered in a variety of ways, including as Mac Egan, Egan, Eagan, Keegan, Keigan, McKiegan, and McKagan.

Tomás Bán Mac Aodhagáin is the name both of a person and of a song inspired by his life. A native of County Mayo, Mac Aodhagain fell in love with and eloped with a Ms. Stanley, daughter of an English settler. Mr. Stanley pursued the couple, captured them, and sentenced Mac Aodhagain to be hung.

O'Rourke writes that "According to folklore, Thomas did not in fact hang; the girl made the song before the sentence was due to be carried out, and the jury was so touched that he was set free. It sounds like wish fulfillment, but even if it were true, her 'provisional lament' would be no less remarkable, as a dramatic presentation of partly imagined events."

A location mentioned in the song is Cluain Aoidh, near Partry. Another individual named in the song, Major O'Connell, was from Newport on the west coast of Mayo.