I've heard 'moke' was a perjorative term for a black person, that it was a shortened version of 'smoke'. I've never found any proof of that, and it may have started with one person saying "I think 'moke' may mean..." and then a bunch of other people saying "I heard it means..."

Webster's New World Dictionary of the American Language, copyright 1966 contains:

Moke [pers. name Moke, applied as pet name to the donkey], [Slang], 1. a donkey; hence, 2 a dull, stupid person.

Now, I haven't met anyone else who remembers the term, but I swear I heard folks use the term 'jamoke' when I was growing up in upstate NY. When I first heard 'moke', I thought it was a shortened version of that. 'Jamoke' seemed to be a friendly insult more than a seriously bad name.