'Scotch songs' are not necessarily songs from Scotland!

‘Scotch Songs’ and English Perceptions of Scotland in the Restoration 14 Sep, 2020 By Allan Kennedy; Dr Allan Kennedy looks at the vogue for Scotland-based popular songs in Restoration England, asking what their subject-matter was, and what they can tell us about English attitudes towards Scotland in the later 17th century.

From Wikipedia; Barbara Allen. A diary entry by Samuel Pepys on 2 January 1666 contains the earliest extant reference to the song. In it, he recalls the fun and games at a New Years party:

...but above all, my dear Mrs Knipp, with whom I sang; and in perfect pleasure I was to hear her sing, and especially her little Scotch song of Barbary Allen.

From this, Steve Roud and Julia Bishop have inferred the song was popular at that time, suggesting that it may have been written for stage performance, as Elizabeth Knepp was a professional actress, singer, and dancer.

However, the folklorists Phillips Barry and Fannie Hardy Eckstorm were of the opinion that the song "was not a stage song at all but a libel on Barbara Villiers and her relations with Charles II". Charles Seeger points out that Pepys' delight at hearing a libelous song about the King's mistress was perfectly in character.