When I reviewed my English lesson, I looked up example sentences. One of those made me was curious that 'It literally rained cats and dogs.'

What does it mean that 'rain cats and dogs'?

l searched the meaning and it means 'heavy rains'

'Why heavy rain is called 'rain cats and dogs?''

So I looked up the origin of the phrase in Google.

It was so interesting.

In old England, they had hay roofs on their houses. And cats and dogs would sleep on the roof. When it rained, the roofs got slippery, and the cats and dogs would slide off of the roofs.

I imagined the situation rains with falling dogs and cats. Well... I couldn't choose the feeling between laughing and pity.