The ballad is also known by the alternative title The Covering Blue, as in Child's 281D version found in Kinloch's MSS from Alexander Kinnear of Stonehaven, in reference to the blue bed-cover under which the girl hides her lover. The Greig-Duncan Collection has more examples with a similar titles; The Coverin Blue (317A) from Mrs Margaret Gillespie and The Coerin' Blue (317E) from R D Reid. These share a verse with some other versions of The Creel in which the old wife declares she had a dream in which the rottens [rats] crept out of a hole in the wall and cut the covering blue, which certainly is one of the most graphic and gruesome metaphors for loss of virginity!

I dream't a dream, it's sine the streen
I hinna wull it be true,
That the rottens cam out o a hole in the wa
En cuttit the coverin blue.

(From the singing of Mrs Margaret Gillespie)

So the 'bonny blue' common to the last verse of most versions of The Creel, is the blue bed-cover which hides the girl's lover from detection; presumably made from blue cloth or wool.

Matthew