I can tell you that the song "The Old Dungarvan Oak" was written by Frank Hennessy, a Cardiff singer who still has a Folk Song Programme on BBC Wales.
He had written a song which Dermot Henry, an Irish singer, had recorded to good sales and he asked Frank for another. Frank had already written "The Old Carmarthen Oak" but had not released it for other artistes o record, so, he merely changed the name "Carmarthen" to "Dungarvan" and that was the origin of this "folk" song. (I hope that I've spelt the name of the Welsh town correctly ?)