What does "OK" actually mean? What is its origin?

There is much controversy over the answer to this question, and no source will give a definitive answer. This is the best we can do given current information:

OK was apparently first used in print in the Boston Morning Post on March 23rd, 1839. It was apparently meant to represent 'Orl Korrekt' ("all correct") - during the late 1830s there had been a brief but widespread craze in the US for humorous misspellings. OK appears to have taken off in popularity the following year during the presidential election {campaign;} Martin van Buren's nickname of 'Old Kinderhook' was shortened to OK.

The Oxford English Dictionary, a publication I have much faith in, endorses this as the most probable explanation.

Wiki has this to say on the topic:

https://en.wikipedia.org/wiki/OK#Proposed_etymologies



Whilst there is a Choctaw word 'okeh' I personally feel that this is not the origin - the good Choctaw people have never managed to get any other word incorporated into the English language!!

Old Kinderhook was a presidential nickname, as Barrow Boy said, and when his signature was needed he intialed it O.K. Soon enough, his secretaries who ask him to OK something and the phrase spread.

I always believed that OK actually was a acronym for 'Zero Kills' from the Battle of Britain in WWII. When the ally pilots landed they would indicate with the 'OK' hand gesture we know today that there were no ally casualties. Hence everything is OK.

I had heard that the letters stood for 'by Order of the King' - meaning the King had endorsed a document.

'OK is a quintessentially American term that has spread from English to many other languages. Its origin was the subject of scholarly debate for many years until Allen Walker Read showed that OK is based on a joke of sorts. OK is first recorded in 1839 but was probably in circulation before that date. During the 1830s there was a humoristic fashion in Boston newspapers to reduce a phrase to initials and supply an explanation in parentheses. Sometimes the abbreviations were misspelled to add to the humor. OK was used in March 1839 as an abbreviation for all correct, the joke being that neither the O nor the K was correct. Originally spelled with periods, this term outlived most similar abbreviations owing to its use in President Martin Van Buren's 1840 campaign for reelection. Because he was born in Kinderhook, New York, Van Buren was nicknamed Old Kinderhook, and the abbreviation proved eminently suitable for political slogans. That same year, an editorial referring to the receipt of a pin with the slogan O.K. had this comment: “frightful letters... significant of the birth-place of Martin Van Buren, old Kinderhook, as also the rallying word of the Democracy of the late election, ‘all correct’.... Those who wear them should bear in mind that it will require their most strenuous exertions... to make all things O.K.'
Taken from https://www.ahdictionary.com/word/search.html?q=OK

Commonly accepted is a Mr. Alan Walker Read's theory that in the late 1830's, when initials and comical misspellings were popularly used in the press, the initials O.K. were published in the Boston Morning Post as a misspelling of All Correct. (Oll Korrect)

During Martin van Buren's political campaign the next year, the phrase, which had become fairly widely used, was taken as an abbreviation for "Old Kinderhook", a nickname given to van Buren. This further entrenched it in the American lexicon.

Of course, it is not known of this is definitely the origin of this phrase. There are other theories out there.

OK, here's a about 20 or so possible theories...enjoy.

http://www.miketodd.net/encyc/okay.htm

1839, only survivor of a slang fad in Boston and New York c.1838-9 for abbreviations of common phrases with deliberate, jocular misspellings (cf. K.G. for "no go," as if spelled "know go"); in this case, "oll korrect." Further popularized by use as an election slogan by the O.K. Club, New York boosters of Democratic president Martin Van Buren's 1840 re-election bid, in allusion to his nickname Old Kinderhook, from his birth in the N.Y. village of Kinderhook. Van Buren lost, the word stuck, in part because it filled a need for a quick way to write an approval on a document, bill, etc. The noun is first attested 1841; the verb 1888. Spelled out as okeh, 1919, by Woodrow Wilson, on assumption that it represented Choctaw okeh "it is so" (a theory which lacks historical documentation); this was ousted quickly by okay after the appearance of that form in 1929. Okey-doke is student slang first attested 1932.



http://www.etymonline.com/index.php?search=OK&searchmode=none

means Ola Kala. which means all right in English.
it came from Greek immigrants who worked on bridge construction in Australia and also in the U.S.of America.

The meaning of OK or okay varies with the context. Basically, it carries approval rather than disapproval ('OK, do it'), or acceptable rather than not acceptable - but less acceptable than 'great' ('The food was great; the service was OK' implies the service could have been better but wasn't bad enough to walk out over). (There is a basic progression from crap through so-so to OK, then great and brilliant. OK is a pass grade, so-so is just a fail.)

Liz seems right on the origins - OK did not originate with Martin van Buren but was hijacked for his campaign. I feel the Boston origin is more likely than the Greek - Greece had only achieved independence from its Ottoman rulers for about ten years, and Boston newspapers and a presidential election campaign are going to have had a wider impact than possible use by Greek seamen (who would probably not have been visiting the US in great numbers as neither country would have much cause for trade with the other). https://en.wikipedia.org/wiki/Okay which covers hopeful's suggestion as well.

The work OK comes from the BRITISH.
It was used as a secret word 'OK' during battles as an abbreviation to 'ZERO KILLERS' <=> '0 Killers'.