Green’s Dictionary of Slang

cornball v.

[cornball adj.]

(US) to make a bad joke; thus cornballing n.

[US]‘Ed Lacy’ Men from the Boys (1967) 108: ‘It was so hot last night I stuck me head in the ice-cube tray,’ I corn-balled.
[US]‘Ed Lacy’ Room to Swing 26: It’s too early for cornballing. What do you want?