Always interesting to learn where sayings derived from...

LIFE IN THE 1500'S:
Sometimes they could obtain pork, which made them feel quite special. When visitors came over, they would hang up their bacon to show off. It was a sign of wealth that a man could "bring home the bacon." They would cut off a little to share with guests and would all sit around and "chew the fat."

Houses had thatched roofs-thick straw-piled high, with no wood underneath. It was the only place for animals to get warm, so all the cats and other small animals (mice, bugs) lived in the roof. When it rained it became slippery and sometimes the animals would slip and off the roof. Hence the saying "It's raining cats and dogs."