Green’s Dictionary of Slang

(US) naïve, unsophisticated.

1947		B. Schulberg Harder They Fall (1971) 237: A gesture right down the fans’ cornball alley.
1957		J. Gelber Connection 24: Will you stop all this cornball stuff.
1961		H. Ellison Rockabilly (1963) 21: That’s pretty damned cornball.
1971		L. Bangs in Psychotic Reactions (1988) 86: The only non-snazz aspect of the set is the cornball liner notes by one Marc Crawford.
1988		P. Califia Macho Sluts 42: Her first words to me were, ‘Do you come here often?’ Some cornball line like that.
1998		Source Oct. 95: The West Coast muthafuckers be on some cornball shit.
2005		Guardian G2 5 May 2: The whole delirious cornball razzmatazz that passes for democratic politics.