O.K. ??

 

On March 23, 1839, the initials “O.K.” are first published in The Boston Morning Post. 

Meant as an abbreviation for “oll korrect,” a popular slang misspelling of “all correct” at the time, OK steadily made its way into the everyday speech of Americans.

Then, there was the gunfight at the OK Corral in October 26, 1881 ... and not much has been "OK" with America ever since!