We say it all the time. Whether using it honestly or sarcastically, we probably don't even think twice about how and where it originally came from.
This two little letters that means your complete agreement with whatever’s being discussed. Or, if you are using it sarcastically by saying it another way, it could also express disagreement or doubt.
The battle for the 'OK'.
For a long time, it was widely assumed that this word was an invention of the USA. But during World War II, Americans came into pretty close contact with other nations fighting both with and against them on their land, and they found out that it wasn’t just an American thing after all. Other countries were also using this word frequently, and also with the same meaning.
Pretty soon, everyone was trying to stake a claim that they were the ones that started it. The Bedouins claimed they first used it while roaming the Sahara Desert. The Germans said it was a reference to a rank in the German military, Oberst Kommandant, and The French said it came from Aux Caynes, a town famous for its rum. Everyone wanted to credit their country with “OK.”
Enter Allen Walker, the 'OK' expert.
A longtime English professor at Columbia University, Allen Walker Read had a long career in tracing the evolution of language.
He found the first use of the word “Dixie” in a minstrel show and “Podunk,” he found, was a Native American term that was used for swampy lands. He also went on record with a powerful statement, saying, “There is no single, monolithic ‘correct English.’ There is nothing inherent or intrinsic that makes language ‘correct.’ ”
He was also the one who finally solved the ''OK" mystery. Professor Read (what an appropriate name for an English professor) found the earliest use of the word in an issue of the Boston Morning Post dated 1839, where the phrase ''o.k. -- all correct.'' appeared. This was during a time when initials and poor spelling like ''oll korrect,'' were the trend.
He also discovered ''KY'' meant ''no use'' (''know yuse''), but that word did not catch on. It apparently didn't have the same ring as "OK". His discovery caused much jealousy by other linguists as they themselves wanted to be the ones to achieve the credits for discovering "OK".
So now we know! It did end up being a US word after all.
Fun fact: Professor Read even wrote the most meta of all words: The definition of the word “dictionary" for the Encyclopedia Britannica. It's like word inception.