Yes I saw that thread, but not necessarily in this case. I think the Joke or Joak was an old form of dance or dance tune, with an unusual bar structure, often 6 bars in the A and 10 bars in the B music. There are Jokes of many colours, including White, Yellow and Brown. And yes, those are the words I know to Constant Billy, plus the chorus
Billy again, Billy again
Billy again, Billy again
They don't write 'em like that any more <G>