Barry's song belongs to that extensive folk genre, the single entendre or not-quite-allegorical song; other good examples are Bo Carter's "Let Me Put My Banana in Your Fruit Basket" or the English ditty "The Bonny Black Hare". It doesn't take a rocket scientist (or even a molecular biologist) to catch the drift...

Ian Robb made an interesting point at a workshop recently that emigrants from the British Isles to the Americas brought over versions of some of the bloodiest ballads and similar songs from home, but a lot of the bawdy ones didn't seem to make it here. The really raunchy American songs tend to be from the blues or homegrown mountain traditions, not the venerable Scots/English smut. I guess today's "moral" standard that blood, gore and violence are okay on TV and movies, but sex is not, is another "traditional family value" that dates back to America's beginnings...