WE SAY it and type it countless times a day, but have you ever stopped to think what “OK” actually stands for?

And is it correct to write “OK” or is it “okay”?

In his 2001 book OK: The Improbable Story of America’s Greatest Word, Allan Metcalf deems OK “the most frequently spoken (or typed) word on the planet — used more often than ‘Coke’ or an infant’s ‘ma’”.

“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,” he wrote.

It was even one of the first words spoken on the moon.

We all know what the word means — it’s a verbal thumbs-up to express agreement — but where does this unique expression come from?

Well, to start with, if you’re going to the trouble of typing two extra characters to write “okay”, you’d be wrong. It’s more correct to write OK because it is actually an acronym.

OK stands for “oll korrect”, or “all correct”.

“Huh?” I hear you ask.

THE HISTORY OF ‘OK’

You know those millennials who type gibberish like “hashtag SHOOK! bae looking goals AF” and bask in their ultra-hip hipness?

Yeah, that trend actually started in the 19th century.

According to Mental Floss, the late etymologist Allen Walker Read traced the word’s origin back to a Boston newspaper in 1839.

Around this time, the editor used it as an efficient, trendy way of saying “oll korrect”, or “all correct”.

It was part of a trend at the time for writers to playfully misspell and abbreviate their words just for the fun of it.

“No go” became “KG” (know go), “all right” became “AW” (all write) and “It shall be done” became “ISBD”.

Of course, trends like this die out easily. No one uses “ISBD” these days, and these days someone will argue even “lol” is better expressed as “haha”.

So how did “OK” survive for almost 200 years?

It was all thanks to the 1840 election campaign of Martin Van Buren, who served as the eighth president of the United States.

According to Read, supporters of the leader formed a club that was affectionately named after his nickname — Old Kinderhook — which became the “OK Club”.

Mr Van Buren’s opponents seized on the trend too, using the term to promote political slogans like “out of kash”, “out of karacter”, “orful katastrophe” and “orfully konfused”.

Basically, whether you supported or opposed the man, “OK” was constantly in your face.

The term might have died after that election (which Mr Van Buren lost), if it weren’t for the advancement of the electrical telegraph throughout that century.

According to Read, the handy little abbreviation was perpetuated as the telegraph became more and more prominent, and by the 1870s, it had become the standard way for telegraph operators to acknowledge receiving a transmission.

After all, it was even shorter than a simple “yes” of acknowledgment.

Read’s version of events has been disputed. Some suggest the phrase drew its origin from the Choctaw Native American language, whose expression “okeh” meant something along the lines of “it is right”.

There are also suggestions it was derived from the Scottish expression “och aye”, the Greek “ola kala” or the French “Aux Cayes”.

Perhaps its sustained use was a combination of all these things.

Regardless, we’re all still using it more than 150 years later, and that’s quite OK by us.

OK: BOTH UNIQUE AND VERSATILE

“OK” is both enduring and unique in our language’s history.

Not to mention, it’s so damn versatile. Observe:

OK: Standard term signifying you are on board with something. Variations include “all right”, “sounds good” and “that’s fine”.

Okay: The modernised American spelling of OK, which also enables its use as a verb: “My editor okayed me to write this pointless article.”

Oooookay: A passive-aggressive expression used to signify the imminent escalation of an argument. It’s also a perfectly adequate response when someone says something vaguely uncomfortable.

Okaaaay: Same as above, but may also signify accepting defeat in said argument, depending on your inflection.

KK: A variation of OK used by tweens of the MySpace era, circa 2005. If you still use this, you now know why you’re still single.

K: You’re either in a hurry, or passive-aggressively expressing your disapproval in a way that conveys you will not tell the recipient why you are no longer speaking to them.

K.: Same as above, only definitely the passive-aggressive latter.

KO: You’re either referring to sport, or you’re drunk. Probably the latter.

The “OK” emoji hand symbol: Your sole purpose is to make strangers viewing your carefully constructed Instagram page believe your life is better than it is.