As it is, the song is a little weird- it talks about three people bathing in a tub together. The song really is about men of respected trades going out to watch women bathe. The original version of the song goes as follows:
“Hey, rub-a-dub, ho, rub-a-dub,
Three maids in a tub. And who do you think were there?
The butcher, the baker, the candlestick maker,
And all of them going to the fair.”
The “fair” was essentially a strip club in the 14th century.