In the 1500’s, most of the houses had a thatch roof. Thatch meant thick straw, piled high with no wood underneath. Little animals would get in the thatch roof to stay warm. All the cats and dogs, mice, rats, bugs and other small animals lived in the roof. When it rained, it became slippery and wet so sometimes the animals would slip and fall off the roof... thus the saying: “It’s raining cats and dog.”
Since there was nothing to stop things from falling into the house, they would just try to clean up a lot. This posed a real problem in the bedroom, where bugs and other droppings from animals could really mess up a clean bed, so they would make beds with big posts and hang a sheet over the top, it would prevent that problem. Hence... ” 4 poster beds with canopies.”