With regard to what Martin Ryan posted a long time ago about the air "Cod Liver Oil", I heard a song on RTE Radio about two years ago with an air similar to this, each verse ending with a line about "Common Blue Clay" (though I think "Common" is actually the name of a place, so it could be spelt in a variety of ways). I think there was a reference to the Kaiser in it, so that would put the date around the time of the Great War. As far as I can rcall, also, it was an agricultural/labour/farmhands' song, not unlike "Rocks of Baun" in feeling. Any farmers will know that there's nothing will grow on blue clay.