Concise and utilitarian, it's quintessentially American in its simplicity. Etymologically, it has no direct relationship with Latin or Greek or any other ancient tongue.
Oxford Dictionaries, on its website, rejects speculation that OK is derived from the Scottish expression "och aye," the Greek "ola kala" (it's good) or the French "aux Cayes," which refers to a Haitian port famous for its rum.
Rather, it favours a theory - shared by Metcalf - that it's an abbreviation of "orl korrekt," a derivative of "all correct" from the 1830s when jokey misspellings were all the rage, like internet memes are today.
Credit for finding its first use in print goes to Allen Walker Read, a Columbia University professor who died in 2002 after a lifetime interest in OK and another widely used word with four letters that starts with the letter F.
It appeared in the Post in the context of an article concerning the ironically named Anti-Bell Ringing Society, founded in 1838 to oppose a municipal law in Boston prohibiting the ringing of dinner bells.
But OK truly entered the national lingua franca in 1840, when spin doctors for Democratic presidential nominee Martin Van Buren, a native of Kinderhook, New York, insisted to voters that it meant "Old Kinderhook."
Today, OK is used "to ask for or express agreement, approval or understanding" or to add emphasis to a sentence, as in "I'm going to stay here, OK?" according to its entry in the Merriam-Webster dictionary.
I'm OK, You're OK, published in 1967, remains one of the best-selling self-help books of all time, while Rodgers and Hammerstein declared Oklahoma in song to be OK! in their eponymous 1943 musical.
There's also the OK Corral in Tombstone, Arizona - but in this instance, OK stands for Old Kindersley and the infamous 1881 shootout that supposedly took place there but actually occurred down the street.
Internationally, OK has travelled remarkably well on the wings of American popular culture - and found a niche in the digital era, fitting easily into 140-character Twitter and text messages.
Using Google Glass eyewear, in fact, calls for a voice command that begins: "OK, Google Glass."
"It's a nice, short abbreviation and it fits abbreviations in other languages," said Metcalf, the executive secretary of the American Dialect Society who teaches at MacMurray College.
"It's distinctive, yet easily pronounced and very readily understood ... It uses the vowel O, the vowel A and the consonant K - and those are found in almost all languages of the world.
"So if you're speaking with somebody who has a totally different language than you, chances are you can get by with gestures and OK in various tones of voice."
- AFP
