> couldn't care less is the phrasing that invokes an expression of maximum indifference
Merriam-Webster asserts both phrasings are equivalent since at least the 1800s.
https://www.merriam-webster.com/words-at-play/could-couldnt-...
Merriam-Webster asserts both phrasings are equivalent since at least the 1800s.
https://www.merriam-webster.com/words-at-play/could-couldnt-...
If you could not care less about an item on that list, that means that it's literally the last thing you would put on list of things you care about. Nothing can be cared about less than this item. Though you could have multiple things at the bottom of your care list, that you don't care about equally. So you can not care less about multiple items on that list.
If you can care less about an item, then there are things on the list that are lower that you do care less about. Making this item not the thing you care about the least. In fact, the item you care about the most... you could care less than that.
> His bearing towards male acquaintances, of whom he knew little or nothing and could care less, was marked by an affectation of gushing friendliness, which overdid itself.