The tune was first known as "The Banks of the Devon", after the words Burns wrote for it. He sasy he collected the tune near Inverness, from a woman singing a Gaelic song, "The Brown Dairymaid". That's a Jacobite song about the '45 written by Alasdair MacMaighstir Alasdair, not long after the event. So the tune must have been in circulation in Scotland in the middle of the 18th century, 50 years before there's any trace of it in Ireland. There's nothing very Scottish Highland about it, it's much like several broadside tunes of mixed Anglo-Scottish parentage you find in D'Urfey and Playford's publications of the late 17th century.

There are *many* Scottish and English broadsides of the early 19th century that call for "The Banks of the Devon" as their required tune, i.e. they got it directly or indirectly from Johnson's "Scots Musical Museum". The Irish balladeers would have got it from the same sources.

Mercury treatment for syphilis goes back to the first ten years of the epidemic, it was standard treatment by 1510. There's lots of 18th century doggerel about it.