I really don't think it's anything to do with the German or Yiddish language,Richard. It's just a different angle on our version. I did a Google to see if there was an answer. Should have done that in the first place, maybe..lol.
Btw. You've added, in the bold print (quote) the word 'cannot' to what I said. I wrote.."As an American would say..I could care less.'
If you scroll down a bit to the post by Bryan Kautzman..ironically.. he gives a good answer which is claiming it's based on sarcasm.
Answer (1 of 260): Fortunately, we don’t see it much in writing, except in novels where the author wants his character to sound colloquial. It probably arose in speech as — oddly — an emphasis. “I couldn’t care less,” through overuse, became too casual and common, so people started saying “I cou...
www.quora.com
I lived in Germany and they say..Es konnte mich (It couldn't. to me) nicht weniger (not less) interessieren (interest) Ie. It coudn't interest me less. That is different to 'I could care less' There's an umlaut over the O in konnte but my iMac won't put one over an O. ..only a U .I get an O with a diagonal line through it as if it were a Scandinavian language.
No idea what it is in Yiddish.
Off to watch the rest of Seville v Man-U