In the UK, they couldn’t care less if you studied Yiddish humor, but in America, we could care less.
I couldn’t care less [THINK: Original UK; idiom]
I could care less [THINK: Yiddish sarcasm; idiom]
“When you want to colloquially express that you don’t care at all about something you might say “I couldn’t care less.” This phrase first popped up in British English at the turn of the 20th century and is still popular today. In the 1960s, a controversial American variant of this phase entered popular usage: “I could care less.””
“…“I could care less” emerged as a sarcastic variant employing Yiddish humor...mirrors the intonation of the sarcastic Yiddish-English phrase “I should be so lucky!” where the verb is stressed.”
“…In English, along with other languages, idioms are not required to follow logic, and to point out the lack of logic in one idiom and not all idioms is…illogical. …not everyone you encounter will be a lexicographer, so be aware that [some]…will cringe if you use “I could care less” in conversation.”
[read more about it on blog.dictionary.com]