NPR : OK and Other Expressions

Morning Edition, March 23, 2007 · On this day in 1839, the expression OK appeared for the first time in a publication — the Boston Morning Post. One possible origin of the phrase is that it was an abbreviation for slang used by teenagers: "Oll Korrect." Other expressions kids made popular at the time: "GTT" stood for Going to Texas and "KY" for "know youse." OK is the only one that survived the centuries.