Do you mean Donal Agus Morag? It's a song recently recorded by altan, on the Blackwaterside album I believe. You may wish to put "altan lyrics" in your search engine and find a lyric site, if the song isn't in the database.

It sounds like "Donal-Og-Us-Morag" when pronounced phonetically, but the spelling is different in Irish.

"Donal, si Donal, si Donal a rinne bhaonis; Donal agus Morag a rinne bhaonis ainmeil." (It's also been recorded earlier by Clannad on the "Crann Ull" album, I believe.)