If you click on the blueish link given by Sophoclese, you'll find lots of verses for the song which skallagrig gives above. The English is a translation from Irish Gaelic. The Lighthouse calls this a Connemara song. Although the best known version is from Connemara, versions of the song have been collected in Munster and Ulster. The other song mentioned by Alliekatt, Donal agus Morag, is quite different. It is found in Scotland and in Rathlin Island. Altan recorded that one (the Rathlin version, with a couple of new verses addes); I'm quite sure it's not on the Clannad "Crann Ull" album.