The origin of O.K.
"...its first known published appearance with its current meaning came in The Boston Morning Post on March 23, 1839: "o.k. — all correct." It appeared at a time when initials, preferably of misspelled words, like "oll korrect," were the fad. "K.Y." meant "no use" ("know yuse"), but that did not catch on."
From the NY Times obit of Allen Read, who also hunted down the source of words like Dixie and Podunk.