Jon and Warren,
Whiskey in the Jar is at least 18thc. A scarce slip song in the Madden Collection entitled Patrick Flemming I would date at about 1785 has 10 stanzas and as with later versions is definitely set in Ireland. This slip was reprinted in the first volume of Holloway and Black's 'Later English Broadside Ballads' p205.

Warren, I will scan you a copy if you wish.

You are right about The Limerick Rake. The earliest copy I have was printed by Brereton of Dublin about 1860 as 'A New Song'. Whilst this was just a sales ploy I would guess it's accurate in this case.

There would have been plenty of English-speaking convicts transported from Dublin at that time so don't feel you have to follow the Irish language course.

If you want to pursue this further access to the Eighteenth Century Catalogue Online (ECCO) would turn up plenty of this sort of material from the likes of W Goggin of Limerick and the Monaghan Press. You won't find much 18thc material in the online collections as the songster/garland format means they are difficult to handle and copy.

Dublin material printed at this time was mostly regurgitated stage-Irish material derived from the London presses.