OK or O.K. or Okay - Most spoken Word in the World
U.S. President Martin Van Buren (A.D. 1837–1841) was born in Old Kinderhook, New York. His nickname, Old Kinderhook, was incorporated into his campaign slogan ("Old Kinderhook is O.K.") and O.K. Democratic Clubs sprung up around the young nation.
Didn't you ever wonder why the word consisted of two capital letters? OK is now widely heard wherever one sets foot on the planet.
Alternative derivations suggest, for example, a play on the dialectal pronunciations of "all correct" by editors of the Boston Post in 1839, but what is sure is that the U.S. Presidential Election of 1836 secured its growing usage.
-- Paul JJ Payack, President & The WordMan
Source : The Global Language Monitor