Taken from Wikipedia: "The earliest printed version gives a rather different picture of the three tradesmen-
Hey rub-a-dub-dub, ho! three maids in a tub, And who do you think were there? The butcher, the baker, the candlestick-maker, And all of them gone to the fair.
'Apparently,' say the editors of The Oxford Dictionary of Nursery Rhymes, 'they have been found in a place where no respectable townfolk should be, watching a dubious side-show at the local fair.'"