1)
Rub-a-dub-dub
Three men in a tub;
And who do you think they be?
The butcher, the baker,
The candlestick maker;
Turn 'em out, knaves all three!

2)
Rub-a-dub-dub
Three men in a tub;
And who do you think they be?
The butcher, the baker,
The candlestick maker;
They all jumped out of a rotten potato,
Turn 'em out, knaves all three!

3)
Rub-a-dub-dub
Three men in a tub,
And how do you think they got there?
The butcher, the baker, the candlestick-maker --
They all jumped out of a rotten potato!
'Twas enough to make a fish [man] stare.

4)
Hey rub-a-dub,
Ho rub-a-dub,
Three maids in a tub,
And who do you think was there?
The butcher, the baker,
The candlestick maker;
And all of them gone to the fair.

The origin seems to be from an old English side-show attraction including three maids in a tub. The rhyme depicts the scurrilous behavior of audience members lacking self-control.