Okay

What is the origin of the word "OK»?
 
There are several versions. Written in any order:

Kelly dined (Obediah Kelly) - US rail freight agent left his initials on important documents to show that everything is in order.
Okeh - Choctaw word meaning "yes»
Orl Korekt (Orl Korect) or Oll Korekt (Oll Korrest) - the popular nickname of the 19th century, US President Andrew Jackson that made him known as DC Jackson (apparently, the use of the funniest comments were extremely popular in the 1830s)
Old Kinderhook (Old Kinderhook) .Preemnik President Jackson, Martin Buren baths, use the "OK" when he spoke of his hometown - Kinderhook.
Ola Kala - the Greek expression meaning "okay»
About Ke - Mandingo language means "all is well»
Wav Kay - the people Wolof means "yes,»
Omnia Correcta - Latin for "the right thing»
Aux Cayes (pronounced as "okay") - a town in Haiti, known for its excellent rum.
Och Aye - on the Scottish means "Oh, yes»
OS - comes from the Latin affirmative «hoc».
It's hard to tell which version is correct - however, I am inclined to 3 and 4. What we can say with certainty is the fact that the president baths Buren popularized its expression, so that in 1840 it was widespread.