The origin of "OK" is actually much more debated and unclear. Here are some of the popular theories:
* "All Correct": This is the most common theory, suggesting "OK" came from a shortening of the phrase "all correct" or "oll korrect" during the 1830s.
* "Old Kinderhook": A nickname for President Martin Van Buren, who hailed from Kinderhook, New York. However, this theory is less likely as the phrase "OK" appeared before Van Buren's presidency.
* Other theories: Some suggest it originated from a Boston newspaper, or even a misspelling of the word "okay."
While there's no definitive answer, it's safe to say no US president is responsible for coining the term "OK."