it is safe to assume that jack campin doesn't read any gaelic or gaidhlig. there are in fact a number of religious songs in both dialects from what gaels call ancient times. they use the word as the French use ancient, as in l'ancien regime. I suspect campin doesn't read French either so for the benefit of the monolingual (and mono syllabic) these old religious songs are found in several sources. the most famous is the seventh century "wexford carol" which has medieval irish words and music. there are many others where the words and tune have separated but a few with both.

ancient regime means before the revolution, so in the gaelteacht that would be before the ascendancy of the English military and churches.

in English translation these religious songs are often called hymns, sometimes carols. they have separate gaelic designations which few here would understand.

I get tired of how the English here on mudcat are experts in everything they don't understand.

so is morning has broken older than 1888 when collected. I think the tune is much older, but i'll have to do some research on it. there are several good on line sources on old gaelic tunes for those with the energy to look around.