Did it start from Orl Korrekt? I've heard that, and that it was an abbreviation used by a general or some such to mean Zero Killed.
Toraneko, different countries display that difference - Americans use it much more for value-free acknowledgement of what you've said than Brits, who see it as meaning agreement. I've seen it cause confusion a few times.
I think we all use it in a multitude of ways, too subtle and slippery and dependent on context and inflection to describe here.
― Martin Skidmore (Martin Skidmore), Tuesday, 17 September 2002 12:28 (twenty-three years ago)