It is...but, it has quite a history behind it. No, I don't remember the details and I can't find the source (it was a book), but it said that the abbreviation "O.K" came during an era where people where obsessed with making abbreviations for everything. A lot of these abbreviations today are unknown because they never stuck. The abbreviation "O.K" stuck because there was an important individual whose initials were O.K during that era and being able to associate this abbreviation with that person's initials made it easy for it to stick in the minds of people.I'm pretty sure OK is just an abbreviation of the word okay..
Like I said, I do not remember the details as this was something faint I
remembered (If anyone has another source, please tell me).
Another crazy origin for a word was the name of a town in Puerto Rico: Aibonito. The name Aibonito came because one of the Spanish came and saw that the land was beautiful, so he/she exclaimed: "Hay, que bonito!" (Translation: Wow, how beautiful!). That exclamation made everyone call it "Aibonito". [The "Ai-" comes from the fact that "Hay" is pronounced "Ai"]
Amazing how such simple things have interesting ways of being born.