Where did "OK" come from?

In the website of Voice of America News by an anonymous narrator, discusses the issue of the origin of the word "ok", http://www.voanews.%20com/ Specifically, she argues that ok is the short term word which stand for an agreement and acceptance. In addition, millions of people use ok eventhough they still dont know where exactly it comes from.
She supports this argument by stating many examples of the various stories which bring up this word to the world. One theory says that it is a short way of writing a different of the word "all correct". The author also claims that ok is an American-English word. This is emphasized when she asserts ok was first using by American people.
Furthermore, she explains that there are many ways to say ok. To clarify this point, the author describes one example from An American series, "The Simpsons," when one character says it another way. He says Okely-Dokely instead of ok to make a better sound. Finally, the author draws the conclusion that the word "ok" is spreading and it becomes the most commonly used word in the world.