No traditional songs about ferrets, I think; though they get a passing mention in some versions of 'While Gamekeepers Lie Sleeping' (Roud 363). There's also 'The Ferrets and the Weasels' (Roud 3558), but only one example (unpublished) has that name; it seems to be a music hall song. I expect there are a few modern songs about putting them down your trousers, and there are certainly some modern dance tunes written more-or-less in traditional idiom that have 'ferret' in the title.