OK, so you're familiar with "OK." You probably use it all the time, and not for just one purpose. But do you really know what it means? And if not, are you OK with that?

The word "OK" is one of America's most popular cultural exports, squeezing myriad meanings from just two letters in a way that embodies American ingenuity, enthusiasm and efficiency. It has almost as many origin stories as connotations, but linguists generally agree the word was first published on March 23, 1839, a date now honored annually as OK Day.

So much subtlety in so few letters has made OK a tough nut to crack. But thanks to the late U.S. etymologist Allen Walker Read, we at least have a grasp on where it came from. After diligent research into OK's history, Read published his findings in the journal American Speech in 1963 and 1964, tracing the term back to a March 23, 1839, article in the Boston Morning Herald (see below).

In the succinct spirit of OK, let's cut to the chase: "OK" is most likely short for "oll korrect," a jokey misspelling of "all correct" that needs a little historical context to make sense. In the late 1830s, a slang fad inspired young, educated folks in Boston and New York to make tongue-in-cheek acronyms for deliberate misspellings of common phrases. This led to arcane abbreviations like K.G. for "no go" ("know go"), N.C. for "enough said" ("nuff ced") and K.Y. for "no use" ("know yuse"). Krazy kids!

The Boston Morning Herald used "o.k." in 1839 This 1839 use of "o.k." in the Boston Morning Herald is now considered the word's first print appearance. (Photo: University of Illinois)

Printing "o.k." in a big-city newspaper helped it rise above other trendy initials, but it soon got an even bigger publicity boost. That's because 1840 was a U.S. election year, and incumbent President Martin van Buren happened to be nicknamed "Old Kinderhook" after his birthplace of Kinderhook, N.Y. Hoping to capitalize on this coincidence, van Buren's Democratic Party supporters formed the O.K. Club to promote him before the 1840 election, according to Oxford University Press.

While OK didn't get O.K. re-elected — he lost to Whig William Henry Harrison — the word did get stuck in America's memory. Its roots were soon forgotten, though, partly due to the same election-year chaos that popularized it. Whigs used it to mock former president and van Buren ally Andrew Jackson, for example, claiming Jackson invented it to cover up his own misspelling of "all correct." Van Buren critics also turned the acronym against him, with insults like "out of kash" and "orful katastrophe."

OK may have been the real winner in 1840, but it still took a while to become "America's greatest word," a title bestowed by author Allan Metcalf in his 2010 book about OK. Top 19th-century writers including Mark Twain shied away from it, according to Metcalf, providing little literary legitimacy until a variant of OK was used in 1918 by Woodrow Wilson, the only U.S. president with a Ph.D.

This long path to ubiquity can be partly mapped by Google Ngram, which charts annual word usage across 500 years' worth of books. It doesn't include spoken OKs, or even all the written ones, but it's still an interesting look at the word's popularity, which apparently surged from 1970 to 2008:

Much of OK's success can be attributed to its brevity and flexibility, according to the Online Etymology Dictionary, which notes "it filled a need for a quick way to write an approval on a document, bill, etc." It has also evolved to fill many other linguistic niches, like granting permission ("That's OK by me"), conveying status or safety ("Are you OK?"), calling to action or changing the subject ("OK, what's next?"), and even hinting at mediocrity or disappointment ("We had an OK time at the party").

The Boston Morning Herald may have been first to print OK, and that instance was clearly decoded as "all correct," but it's still impossible to rule out many alternative origins. Woodrow Wilson argued it should be spelled "okeh," for instance, because he thought it came from the Choctaw word okeh for "it is so." That's a longstanding explanation, but its support has faded due to lack of evidence.

Other theories also see shades of OK beyond American English, in terms like Scots' och aye ("yes, indeed"), Greek's ola kala ("all is well"), Finnish's oikea ("correct") and Mandingo's O ke ("certainly"). Complicating matters is that some people now spell OK "okay," a newer variant. Even in the acronym camp, though, some argue OK came from the shorthand for "zero killed" on battlefield reports.

Oxford describes a potential link from OK to West Africa's Mandingo language as "the only other theory with at least a degree of plausibility," but adds that "historical evidence ... may be hard to unearth." As with much of U.S. culture, OK could just be a blend of concepts and syllables from around the planet, slowly gelling over generations. Whoever coined it, it's now widely used as a loanword in other languages, providing a pithy verbal package for what NPR calls "America's can-do philosophy." And with that much global reach, OK has probably grown too big for us to ever dig up its roots.

That may not be a very satisfying answer, but considering all that can happen in 175 years, it's OK.