This strange, somewhat surrealist phrase has a contested origin. It dates back to at least 1651, and it might have to do with dogs and cats symbolizing wind and rain, respectively, in different mythologies. Another possibility is that it’s a mangled form of obsolete words, either the Greek cata doxa (meaning “contrary to experience or beliefâ€), or the old English catadupe (“waterfallâ€).None of those explanations have conclusive evidence to support them, but they’re all plausible. One theory that’s been totally busted, however, is the idea that cats and dogs would huddle in thatch roofs during storms, and the rain would wash them out. For that to happen, the animals would have to be on the outside of the roof, which doesn’t track.