could or couldn't

[Cayenne]

Help a Swede, someone. There's an expression that goes I could care less. It means I couldn't care less. What's the explanation for that paradox? Is there some part 'missing' from some original expression? Like, I could care (even) less (for your problem if I were a zombie). Thanks!

[Peter Pedant]

no its

I couldnt care less

and means I do not care at all,

nada, niet, nichty nichty

 

I have not heard 'I could care less' in this sense. Words do reverse their meanings - that is they take on a second sense which is opposite to the main sense. (!)

dyke means a ditch as well as a wall, (and of course a girll on a bike) - but this is not an example [in Manchester]

[smorodina]

Americans say 'I could care less', but it's used in a sort of ironic way - 'do you think I could care less?' The British always say 'I couldn't care less.'

[corosanta]

"I could care less" means that there is a possibility that you could, in fact, care less about the subject if you really put your mind to it. "I couldn't care less" means that you think the subject unworthy of any more thought.

[Marsh]

There's more information at http://www.worldwidewords.org/qa/qa-ico1.htm 

[Laurinha]

I think if someone says 'I could care less'  then they actually care quite a bit about whatever it is!