While living in Germany I came across a reputable reference as to the origin of this word. The dating of it is traced back to the 9th century and it specifically references the initials of King Otto (Otto Konig) of what is today Germany. This pre-dates anything written in your article which seems to elude to the reference being strictly born in an English speaking environment.
The story is that when Otto (Konig) gave his permission on what ever topic required his attention, he would indicate it so by signing and wax sealing his answer with his initials “OK”, short for “Otto Konig”.
In other words, the roots of this expression are European and not born anywhere in the English language.
[list=I][li]This would presumably be in reference to What does “OK” stand for?[/li][li][LIST=A][][ol][/li][li]Have you any evidence whatsoever that anyone in the history of the world ever bore the title “King of Germany”?[/li][li]Have you any evidence whatsoever that any King of Germany was named Otto?[/li][li]Have you any evidence whatsoever that any King Otto of Germany ruled in the 9[sup]th[/sup] century?[/li][li]Have you any evidence whatsoever that this supposed 9[sup]th[/sup]-century King Otto of Germany signed documents “Otto König”, and not “König Otto”, or simply “Otto”, or “Otto Rex”?[/li][li]Have you any evidence whatsoever that anyone continued to sign documents “Otto K̈onig” or “OK” after the death of this supposed 9[sup]th[/sup]-century King Otto of Germany?[/ol][/li][li][ol][]Have you any evidence whatsoever of this usage existing in the English language prior to 1839?[/li][li]Have you any evidence whatsoever of this usage existing in the United States prior to 1839?[/li][/ol][/LIST][/LIST]
Well, it looks like there was a Otto who among other things was titled king of germany, in the 10th century.
However, the second link when you google king otto ok, is this page. And the other links are nothing to do with the origin of the word “OK”.
It doesn’t seem that this theory has gained much acceptance. Or awareness.
Yes, but he was that only by virtue of holding the vastly superior title of Holy Roman Emperor. He would have signed with the title of “King of Germany” about as commonly as Her Majesty today signs herself “Elizabeth, Lord of Mann”, or “Duchess of Normandy”.