Jack, they might be quite rare in Scottish manuscripts but RAMSAY's Tea-table Miscellany is full of them taken directly from the London playhouses. (including Barbara Allen).

The use of 'Scotch' does not necessarily equate to pseudo-Scottish; it was used to describe a general perceived dialect used anywhere north of Watford, apparently. Most Londoners had little experience of the language used outside the greater London area in the 17th century.