Where did the expression "it's raining cats and dogs come from?"

In England during the seventeenth century, thousands of cats and dogs
ran wild in the streets. These streets also had no storm drains.
During heavy rains, a number of these wild animals would drown, and end
up floating down the streets in the ensuing runoff. This gave the
appearance that it had indeed "rained cats and dogs" and led to the
current expression.