We use it to describe how we're feeling, if we agree, or even just to start a sentence — the word "OK."
But what do these two letters really mean, and why do we use them so often?
One theory claims OK abbreviates "oll korrect," a bastardized spelling much like N.C. for "nuff ced" and K.Y. for "know yuse" in the 1830s. Think "ZOMG" or "LOLZ" today. And that's how OK first appeared in 1839 in The Boston Morning Post: as a joke, according to Alan Metcalf in his book, "The Improbable Story of America's Greatest Word." The term celebrated its 175 anniversary on Sunday, March 23.
While he didn't coin the term "OK," eighth President Martin Van Buren popularized it. His supporters began referring to themselves as the "OK Club," OK being short for Old Kinderhook, Van Buren's nickname based on his birthplace: Kinderhook, N.Y. Some claim Van Buren started writing "OK" as his signature on official documents.
In 1919, Woodrow Wilson, claiming the word came from Choctaw language, spelled it as "okeh," later ousted by the modern spelling "okay."Pete Seeger, the recently deceased political folk singer whose songs often told tales of language, also claimed "okay" originated with Choctaw.
Cyrus Byington's "Dictionary of the Choctaw Language" in 1915 gives the earliest evidence of that. As a Christian missionary working with the Choctaw in Mississippi, Byington cataloged the people's language extensively. According to him and even dictionary's published later, "okeh" meant "it is so and in no other way."
So the choice comes down to a Native American etymology or an American one. And the word's origins could play into the spelling controversy.
Some style guides, such as the Associated Press, insist on the spelling "OK," but most accept "okay" as informal use.