Presumably you've read the thread. We don't know who wrote it (though that information may perhaps turn up one day), but the middle of the 19th century seems likely; though, as stated, it was based on an earlier broadside song (which in turn was based on real events) of which forms have been found in oral currency in the USA and Canada.

Although the original events took place in Ireland, the music hall song would appear to be British, and the refrain meaningless and made just to sound "typically" Irish to non-Gaelic speakers; though of course we can't be certain of that. Look also at the late Bruce Olson's website (mentioned earlier) for more on the Patrick Flemming broadside: Patrick Flemming.