That's my analysis too.

Lloyd's version (origin unknown - and I'm afraid we know what that means) has "ring-tailed" and "come up behind."

Since the minstrel lines that apparently inspired the lyrics are "clean," I feel that the clean versions of the shanty are closer to the original and that the dirty versions are parodies. They could have been created at any time, though, including ten seconds after the shanty was first sung.