The Oxford Dictionary observes there have been many attempt to explain the origin of this expression, and most of them are speculations with little historical evidence to back them up. The expression became popular in the mid-1800s, and is likely to be an abbreviation of orl korrekt, which was invented to be a “jokey misspelling of ‘all correct’.” Supporters of President Martin Van Buren called him “Old Kinderhook” after his New York birthplace and formed the “OK Club,” which helped popularize the expression OK to indicate all is well. Another theory is that black slaves had a term for “all right, yes indeed” in various West African languages which apparently sounded like OK. The explanation ends by saying “…historical evidence enabling the origin of this expression to be finally and firmly established may be hard to unearth.”