Hi Jim,
Good to hear from you again.
Got any research on at the moment?
I've just been reading the spats between Chambers (1849) and Clyne (1859) and Lang's apologies for Scott/Hogg (1910). Whilst I think Chambers had a point about the age of the ballads, Clyne was right to question his attribution of the 25 to Mrs Laidlaw. They were quite likely written by her contemporaries or even later.

I've searched through Farmer and D'Urfey for 'sketches' and even the Oxford Dictionary, with no luck. I think a really good cant dictionary might help. The more likely source would be finding it in another ballad.

Whilst there must have been other printed versions and the earlier one doesn't have this verse, it was printed by Pitts, Catnach, and Morren of Edinburgh in identical forms (this verse) so this rewrite could be c1800-1820.