These lyrics are from the Nursery Rhyme ‘Rub-a-dub-dub’
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Answer:
The Boxer Rebellion occured because many European contries were selling illegal drugs like opium to Chinese citizens. A group of Chinese citizens formed and became the Boxer Rebellion. They fought against the marketing of drugs like opium and heroin that were being widely sold and bought in China.
They were warning the town that the British were coming to attack.