Old post, I know, but I just came across here somehow and wanted to share an old 1962 paper I came across recently about the origin of "O.K."

There was a Boston fad of, what Allen Read calls, "humourous misspellings" and abbreviations. O.K was likely formed from a humourous misspelling of "Oll Korrect"

"The author who popularized misspelling as a humorous device in America was George W. Arnold (I783-I838), who wrote letters under the pen name "Joe Strickland" from 1825 to 1830. The following passage is characteristic:

Konstanty Nople, Jennywerry, 1828

Deer & lovin unkle Ben,

I spoze you thort kaze I was so darn fur of that I wasnt goen tu rite yu agin. but iph you think I kan evver forgit yew, ur Ant Nabby yew are tarnally mistaken, kaze I should remember yew iph I waz tother side ov awl1e kreashun. not by a darn site-un iph I evver git Bak agin i'll be hang'd if yew evver ketch me in this kutthrote kuntry agin. taint half so good as oald Varmount-I kum plaigy neer starvin tu deth afore I got here, we hadn't northen under hevven tu ete haff the time only Dry Kod fish un taters-finally and tarnally arter an evverlastin long pasage we got heer. i'de bin see sik awl the time, un had pritty neer spewd my gizard up, til by the lord harry I wa'rnt much bigger round than Dekon Bigalows pichfork handel-when I got hear tha axt me if I was evver in Turky before, no ses I. but i've had a darn menny turkys in me-i'de aleys heerd a plaigy deel about, Turky in Urop, in the gogfry when I went tu skool tu Ikabud Krane, whare I larnt tu Spell-un by the jumpin jingo my mouth wartered az soon as I landed.""

The entire paper is definitely a fun read and I highly recommend checking it out!

Read, Allen W. (19 July 1941). "The Evidence on O.K.". Saturday Review of Literature.