Corny

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1930s: from an earlier sense ‘rustic, appealing to country folk’.

wiktionary

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From Middle English corny, equivalent to corn +‎ -y. In the "hackneyed" sense, from "corn catalogue jokes", reputedly low-quality jokes that were formerly printed in mail-order seed catalogues.

Latin cornu(“horn”).

etymonline

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corny (adj.)

1570s, "full of corn, pertaining to corn," from corn (n.1) + -y (2). Chaucer used it of ale (late 14c.), perhaps to mean "malty." American English slang "old-fashioned, sentimental" is from 1932 (first attested in "Melody Maker"), perhaps originally "something appealing to country folk" (corn-fed in the same sense is attested from 1929). Related: Cornily; corniness.

There's an element of truth in every idea that lasts long enough to be called corny. [songwriter Irving Berlin (1888-1989), in a 1962 interview]