there are lyrics in Irish for several O'Carolan tunes in James Hardiman, Irish Minstrelsy or Bardic Remains of Ireland (1831, facsimile reprint Irish University Press, 1971)
and in Douglas Hyde/Dubhlas de hÍde, The Songs of Connacht, Amhráin Chuig Chonnacht edited by Breandán ÓConaire published 1985 based on de hÍde's late 19th -early 20th century collections. Tunes aren't given, so in some cases where titles vary it would be hard to know which tune goes with which lyric. I wonder why we don't hear more of the O'Carolan lyrics sung. But that would hold for some other songs as well, for instance The Coolin is heard far more often as a slow air than as a song.