It has been so hot and muggy that the cats are just lounging around listlessly. Which means…well, the word seems to suggest that they don’t have any lists. I’ll admit that cats aren’t big list-makers (though they are otherwise fine creatures), but we know that that’s not what the word really means.
Why doesn’t “listless” mean “without lists”?
Naturally I looked it up. It turns out that this “list” is an entirely different word: it’s from the Middle English “list”, meaning ”desire” and cognate to “lust”.
So the cats were really lying around lustlessly, which seems apt.