Hi GUEST
The song referred to was 'Scotch' not 'Scots'. I have it on reliable historical authority that the word 'Scotch' was used in 17th/18th century London to describe any song that used pseudo dialect from anywhere north of Watford. It was similar to what we might call 'stage Irish' nowadays. Or 'Bumpkin'songs of the 19thc. They were mostly written in London using pseudo dialect and often written for plays and pantomimes.

It always reminds me of the so-called Scots version which as Richie says featured heavily in anthologies but is rarely given from oral tradition and when it is it varies very little from the book version. I have no proof for this at all. Just a hunch.