TO RAIN CATS AND DOGS, sometimes extended to AND PITCHFORKS AND SHOVELS, phr. (popular).—To rain heavily. [The French catadoupe, a waterfall, has been suggested as the origin. Another etymon has been found in the Greek κατὰ δόξαν in reference to the downpour being out of the common. Possibly Swift, who seems to have been the first to have used the expression, may have evolved it out of his own description of a city shower (1710).

          Now from all parts the swelling kennels flow,
And bear their trophies with them as they go….
Drown’d puppies, stinking sprats, all drench’d in mud,
Dead cats, and turnip-tops, come tumbling down the flood.]

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  1738.  SWIFT, Polite Conversation, dial. 2. I know Sir John will go, though he was sure it would rain CATS AND DOGS.

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  1819 (Feb. 25).  SHELLEY to PEACOCK, in Letters, etc. (Camelot), p. 264. After two months of cloudless serenity, it began raining CATS AND DOGS.

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  1837.  R. H. BARHAM, The Ingoldsby Legends (The Blasphemer’s Warning).

        But it ‘rains CATS AND DOGS,’ and you’re fairly wet through
Ere you know where to turn, what to say, or to do.

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