Okay (OK) is a colloquial English word denoting approval, acceptance, assent, or acknowledgment. OK is most likely short for “Oll Korrect,” a jokey misspelling of “All Correct” that needs a little historical context to make sense.
There have been numerous attempts to explain the emergence of this expression, which seems to have swept into popular use in the US (United States) during the mid-19th century. Most of them are pure speculation.
It does not seem at all likely, from the linguistic and historical evidence, that it comes from the Scots expression och aye, the Greek ola kala ('it is good'), the Choctaw Indian oke or okeh ('it is so'), the French aux Cayes ('from Cayes', a port in Haiti with a reputation for good rum) or au quai ('to the quay', as supposedly used by French-speaking dockers), or the initials of a railway freight agent called Obediah Kelly who is said to have written them on documents he had checked.
The word OK is an abbreviation of ‘orl korrect’. It was coined in the USA and means ‘all correct’. The word was first used as a slogan during the presidential re-election campaign of Martin Van Buren (1782–1862) in 1840. Van Buren’s nickname was “Old Kinderhook”. Back then, in Boston and New York abbreviations were the rage and words were misspelled deliberately. So a group of his followers called themselves the “O.K. Club”; this later went on to mean “oll korrect” and “Old Kinderhook”.
OK is just one of the many slang words that have survived till today.