Who knows the origin of' throwing shit'?

This word comes from hk, because most people can speak English, and there is a slang: it's raining cats and dogs. Use him to describe the rainstorm. In the past, when it rained heavily, the bodies of cats and dogs would float on the river, so it was a joke that cats and dogs fell from the sky. And Hong Kong people, with this sentence, expressed their hatred of heavy rain more vividly. I think heavy rain is worse than stepping on dog shit. So, shit.