The story
No one knows for sure where this one came from. That hasn’t stopped people from guessing.
The most popular story says that long ago, cats and dogs slept in thatched roofs and slid off when the rain got heavy. It spread widely by email around 1999, and it falls apart quickly. Dogs don’t climb onto roofs, and no animal sits out on wet thatch in a storm.
What is certain is that English writers have long dreamed up wild rain. In a 1653 play, Richard Brome promised that “It shall raine … Dogs and Polecats.” In 1738, Jonathan Swift had a character say “I know Sir John will go, though he was sure it would rain cats and dogs.” That is the phrase in its modern form.
Swift may have had a picture in mind. In his 1710 poem “A Description of a City Shower,” London’s gutters overflow and “Dead Cats and Turnip-Tops come tumbling down the Flood.” City streets of the day could wash all sorts of things along in a downpour. Another idea is simpler: cats and dogs are famous for squabbling, so the phrase may just mean the weather is behaving badly.
Other theories point to a French word for waterfall or to old myths. None has any evidence behind it. The true origin, as The Phrase Finder puts it, “is now lost to us.”
