This page at the Contemplator site says that Gaelic lyrics to "Sheebeg and Sheemore" are given in the book "Carolan: The Life and Times of an Irish Harper" by Donal O'Sullivan, published by Celtic Music, Louth, Lincolnshire, England, 1991, (First published in 1958).

It isn't clear from the information on this web page whether Carolan wrote the lyrics, or whether he only wrote a tune to go with an existing poem. The story concerns a battle between two faeries.