As we all know cats were Gods in ancient Egypt. As this did not work out with the upcoming monotheism in Mesopotamia they got reduced from immortal to six lives. But on their way north towards Europe life got rougher so they gained a seventh life to compensate for that. And finally coming across the channel to work with the witches (and Shakespeare) they upgraded to nine lifes to compensate for the additional danger.
Cats are still Gods.
/cc @GreenSkyOverMe