'"Star of the County Down" is an old Irish ballad set near Banbridge in County Down, in Northern Ireland. The words are by Cathal McGarvey, 1866-1927, from Ramelton, County Donegal.' Wikipedia
[btw - aka Cathal Garvey]

Funny that this well-known attribution appears nowhere on this thread - it probably appears on some of the others, but it should surely have been mentioned. The tune is, of course, related to the 'Dives & Lazzarus' family.