It's raining cats and dogs!

Someone said to me today, '...oh it's just one of those things...', after a pause for thought, the question crept up on me, 'one of what things?'

We use these phrases in every day language, because we've learnt them...but have we ever really questioned them?

'It's raining cats and dogs' - Apparently, in tornado's, the debris that gets sucked up and spun around wildly, including cats and dogs, fires right back down onto land when the tornado dies down. Therefore, as the cats and dogs seem to be falling from the sky, it looks as though it is raining cats and dogs!