I have spent the last five minutes thinking about the etymology of the word ‘ok.’ When I was very young, I read in a magazine that it was popularized in the 1920s as a joke, as an acronym for the phrase ‘Oll Korrect.’
Unfortunately, I can’t come up with anything more reasonable.
As I understand, it comes from the initials of a failed presidential candidate in the late 1800s. I forget exactly when or who. Wikipedia, as always, has more info.