Why do we say 'raining cats and dogs'?

There are also two theories suggesting the renowned Irish satirist Jonathan Swift made the phrase popular. In 1738, in his Complete Collection of Genteel and Ingenious Conversation, a character is afraid it might “rain cats and dogs”. It’s fairly likely that Swift’s satire, regardless of whether he invented the term, was responsible for its following popularity. In 1710, Swift wrote the poem, City Shower, which included an image of dead animals left in city streets after heavy floods.

Not that this really answers why cats and dogs, of all animals. There are four possible origins of why the domestic pets became synonymous with torrential downpour. They are…

1) Cats and dogs used to cuddle into thatched roofs during storms, only to be washed out during heavy rains. Considering how a well-maintained thatched roof is actually fairly waterproof, the animals would have to be cowering on the outside, so this wouldn’t have been a great hiding place in a storm. This theory makes for a nice story, but is probably apocryphal.

2) In Norse mythology, Odin, the father-god responsible for storms, was often depicted with dogs and wolves representing winds. According to folklore, witches rode their brooms during storms, accompanied by their black cats, so that image took on the connotations of heavy rains for sailors. Odin and witches could be responsible for the expression.

We may have the words entirely wrong, and instead we should be saying ‘cata doxa’

3) We may have the words entirely wrong, and instead we should be saying ‘cata doxa’. This Greek expression means ‘contrary to experience or belief’, which an actual storm featuring falling cats and dogs certainly would be.

4) Finally, we could be using a derived form of the now-obsolete word ‘catadupe’. In old English, this meant a cataract or waterfall. Versions of this word existed in many ancient languages, like the Ancient Greek κατάδουποι, referring to a cataract of the River Nile. So when we say it’s raining cats and dogs, we might be suggesting that it is raining waterfalls.

• Read more about the ancient Greek alphabet

We will probably never know the exact origin of the phrase, but the eccentricity of the image behind it adds to the creative, unpredictable nature of English as a language.

This article was taken from BBC History Revealed magazine