OK or sometimes called, Okay is a colloquial English word denoting approval, acceptance, assent, or acknowledgment.
This is most likely short for “Oll Korrect,” a jokey misspelling of “All Correct” that needs a little historical context to make sense.
The origin of OK is historical, it is claimed by researchers that written records of the term OK is found as back as early 1800’s.
It had been understood that the expression gained popularity soon after when it was used as the name of a political organization, called the O.K. Club. That is, the letters may have originated from the letters stood for the birthplace of President Martin Van Buren—Old Kinderhook, NewYork.
Sone researcher claims that it originated during a war when the soldiers from the war front called for back from the reserve, they would just send a message on the telegraph – 4.K. meaning 4 soldiers were killed and 0.K. meaning no-one was killed that day.