Oops, forgot the line breaks - sorry.

Weepiper, you may be on to something, the melody for each of the first three lines is very similar, with small variations.

Agus seoithin Agus seoithin Agus seoithin Agus seo
Agus seoithin Agus seoithin Agus seoithin Agus seo
Agus seoithin Agus seoithin Agus seoithin Agus seo
(something else in gaelic - can't make it out)

Brian, the singer is Padraigin Ni Uallachain, with Garry O Briain on keyboards, from an album entitled A stor A Stoirin. I have it as part of a compilation tape called Celtic Lullaby. I like the singer, so I may end up buying the source album and maybe that will have some info. But althing you can tell me now would be much appreciated.