Actually, burying a cat within your wall was most likely practiced by more than a few back in those times. Yes, it was probably to ward off bad spirits or something to that effect. No, it doesn't absolutely mean that witches lived in that dwelling. A dead black cat was found lodged purposefully within the walls of the Tower of London. It had been buried there possibly withing the same time frame of the 1600's. This factoid is verified (and shown) in the BBC documentary "The Tower". (www.imdb.com/title/tt0756275/)