To hark back to John's long list of versions in the Roud index, the earliest version I have 'Johnny is a Handsome Man' was printed by Armstrong of Liverpool 1820-24. There are at least 2 versions of this printing on the Bodleian site. Quite a few of Armstrong's printings came from Irishmen arriving in the city, and spread out from there across the rest of the UK to other printers, being developed on the way, pieces like Molly Bawn, Willie Leonard, Fanny Blair, Strands of Magilligan. The Irish origin is at least a possibility.