What is "rub-a-dub-dub"

"Rub-A-Dub-Dub" is an English language nursery rhyme first published at the end of the eighteenth century in volume two of Hook's Christmas Box under the title "Dub a dub dub" rather than "Rub a dub dub". It has a Roud Folk Song Index number of 3101.

Rub-A-Dub-Dub was a British nursery rhyme TV series animated by Peter Lang and Alan Rogers of the Cut-Out Animation Co. They were previously famous for Pigeon Street. The series was produced by David Yates and Joe Wolf. The title is a reference to the nursery rhyme Rub-a-dub-dub. Rub-A-Dub-Dub was animated in a similar way, yet all the characters were anthropomorphic animals. It ran in 1984, completing 25 episodes.