The sudden appearance of O. K. in 1839 and its rapid spread argues for a unique coinage, which is supported by the newspapers and speeches of the time as well as a consensus of scholars who have studied the term.
Students of language are well aware of possible preceeding forms; this is a part of language study.

Och is an old exclamation, Ah!, Oh!, Alas!, known in both Ireland and Scotland. Och, Lord! and Och, how? are both early, as well as just plain Ochs! and Och!. There is no known DNA connection to 'hoc.'

I was hoping someone familiar with the history of Och, aye! would comment here.
Ay, aye, I, early forms ai, ei, etc. has an obsolete dialect meaning of ever, always, which bleeds over into och aye (Ah, ever so!, That's right!, right on!, etc.) Someone who has studied the Scottish and northern English material would be much better qualified to comment than me.

In a recent study of speech in Texas, it is noted that oil is pronounced 'all,' but the pronunciation is disappearing in the cities.
Can't remember if Hagler pronounced it 'correctly' in the old TV series (No relation to the all in all correct).