Raining cat and dog...

Last few days I see few people using this idiom...so I go search for it...why is call Raining cat and dog...

Rain Cats and Dogs

This phrase's origin is unknown. Possible explanations include: The archaic French cantaloupe is a waterfall or cataract, lightning and thunder sounds like that of a cat/dog fight, cats had a big influence on the weather, and the sky dog Odin was attended to by wolves according to Norse Mythology.

Another theory is that in old England, they had hay roofs on their houses and the 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. There for it was "Raining Cats and Dogs".

This from a website visitor:
"raining cats and dogs" came from the middle ages, when houses had thatched roofs. To keep warm lots of animals would hide in the roofs when it was raining and sometimes fell through the flimsy roofs on to the streets below.

This from another website visitor:
I do believe the idiom "Rain Cats and Dogs" stems from the Norse Mythology. Cats were believed to represent the wind and dogs represented rain. Different animals represented different weather and natural phenomenon

This from another website visitor:
For the Idiom "Rain Cats and Dogs" I have heard one other explanation. In old England when peoples cats and dogs died they would simply through them into the gutter or alley with the garbage. If a strong enough rain came through it would flood the gutters and alleys to the point where all the dead cats and dogs would begin to float down the streets. Therefore very harsh rains were associated with cats and dogs.