It’s a word I’ve used many times as an alternative to “dude” or “person,” I’d never seen it in print until today at Three Jamokes and a Car | Shorpy Historical Photo Archive.
According to Wiktionary:
Appearing at the end of the 19th century as a blend of java and mocha, by the 1920s it became slang for someone who lacked mental abilities beyond that of a cup of coffee, probably influenced by moke. In the 1930s it also First appeared in the Old Italian Neighborhood of Chicago Southwest Side of “69th and Ashalnd” in the early 1930’s. Considered to be a True Chicago Lingo word.
I’ve been speaking True Chicago all my life and didn’t know it!
… I think I learned it from Bugs Bunny.