“I could care less” is a bastardization if couldn’t care less. I have no source but I sincerely doubt “could care less” was the original usage.
Another one is the pattern “all X are not Y.” Vs “not all X are Y.”
Another one is the pattern “all X are not Y.” Vs “not all X are Y.”
> “I could care less” is a bastardization of couldn’t care less.
I've come to the conclusion that this bastardization came from the way "--dn't c--" feels in the mouth. Lots of consonant sounds in a row. Drop the "n't" and it feels much better to say, even though the phrase becomes nonsense. You even get a little bonus alliteration.
https://www.nytimes.com/1979/09/30/archives/on-language-twow...
https://www.grammarphobia.com/blog/2007/01/i-could-care-less...