"OK" is certainly one of the most common expressions in the English language--and one of the most versatile. After all, it can be used as an adjective, a noun, and a verb.

But what do the letters in OK stand for? And where did the expression come from in the first place?

Over the years, a variety of explanations have been offered. Some have argued that OK came from the Native American Indian tribe Choctaw's word "okeh." Others have suggested it came from a word in the Wolof language of Sub-Saharan Africa.

The expression gained popularity soon after when it was used as the name of a political organization, called the O.K. Club. That is, the letters may have originated as an abbreviation for "oll korrect," but in this case the letters stood for the birthplace of President Martin Van Buren--Old Kinderhook, N.Y.

"Read points out that the trajectory of the term was affected by its adoption as the moniker for Martin Van Buren ('Old Kinderhook')," Horn explained in the email. "So Van Buren and his supporters didn't create the term, but kept it very much alive."

Horn said that many other satirical abbreviations got their start around the same time as OK but are no longer used--including K.Y. for "know yuse," K.G. for "no go," and O.W. for "oll wright."