I'm sorry I can't help with the song, but if you're using search engines you'll have better luck if you spell the names MacSwiney and MacCurtain. Terence MacSwiney and Tomás MacCurtain were mayors of Cork and their stories are well known, as Google will attest. There's a bronze bust of each one on the steps of City Hall, which I walk past every week.

If you find these words, please post - both men have compelling stories. (Síle MacCurtain, daughter of Tomás and witness to his murder, played harp.)