Johnny Raddlum somewhat misses an important point covered by other versions, that the wife is pregnant, which is said to be the reason why she sends the man out for the crab in the first place.
Jim Carroll

From Mrs Overd's version, The Crabfish' collected in Somerset by Sharp

"Her belly it grew big and all she did wish
Was to get a taste of a little crabfish,
With me row dow dow, diddle al a day,
With me row dow dow, diddle al a day.