Growing up as a JW, I was told that KISS stood for Knights In Satan's System (or Service).
I just did a Google search and learned it's not true. It's actually not an acronym for anything.
To be honest, apparently it's not just the JWs who believe it means something related to Satan.
One day Paul [Stanley] and Peter [Criss] and I were driving around, brainstorming for new names. I had thought of a few, like Albatross, but I wasn’t happy with any of them. At one point — we were stopped at a red light — Paul said, “How about KISS?” Peter and I nodded, and that was it. It made sense. Hindsight is 20/20, of course, and since then people have talked about all the benefits of the name: how it seemed to sum up certain things about glam rock at the time; how it was perfect for international marketing because it was a simple word that people understood all over the world. But we just liked the name, and that was that.