Incidentally, I've just managed to dig out Robert Cinnamond's version of this song; as with Packie Russell's, it does not have a repeated verse at the end, nor is it particularly bawdy, so unless there is another version of it we can't find, the one that was sung around the clubs was an entirely 'revival' creation - no harm in that, just a confirmation that the repeated line has nothing to do with how it was sung in the tradition.
Jim Carroll