I have once heard of a story about it in an opening English class in my days of being a freshman. But i can't recall it quite clearly. " it is raining dogs and cats" is probably an idiom in English. Perhaps it dates back to the Middle Ages in England, when and where people were poor and there are not abundance of food supply. Many wild cats and dags had to hang around in the streets or alleyway for food at that time. However, there would be less food resources on rainy days,When encountered with continuous rainy days, the wild claws had to suffer a lot from hanger and coldness. With nothing to eat, many of them became weak and even starved to death or died of other unknown diseases. One day when local residents opened their windows seeing dead bodies of those poor creatures here and there out of the doors in the streets, It seemed as if the dead anumals happened to drop down with the heavy rain.

everyone knows it means raining heavily but its hard to say where does it actually come from? infact, there is no clear evidence of its origin... there might be alot of different explainations but no known facts... here r some links for ur reference: http://www.worldwidewords.org/qa/qa-rai1.htm http://www.phrases.org.uk/meanings/raining%20cats%20and%20dogs.html

It has been suggested that at one time the streets of British towns were so poorly constructed that many cats and dogs would drown whenever there was a storm; people seeing the corpses floating by would think they had fallen from the sky, like the proverbial rains of frogs. ALSO It seems that cats were at one time thought to have influence over storms, especially by sailors, and that dogs were symbols of storms, often accompanying images and descriptions of the Norse storm god Odin. So when some particularly violent tempest appeared, people suggested it was caused by cats (bringing the rain) and dogs (the wind).

I know this meaning ) I want to know etymology

"It was raining cats and dogs" means "it was raining heavily." I don't know why "cats and dogs" are used.