As for “corny,” meaning trite, overly sentimental or schmaltzy, we can probably trace the term to, believe it or not, the mail-order seed catalogs popular in turn of the century America. To hold their customers’ interest, seed firms would sprinkle jokes, cartoons, stories and riddles throughout their catalogs. The jokes, being of singularly low quality, came to be known as “corn catalog jokes,” which was then shortened to simply “corny” and eventually applied to anything considered embarrassingly unsophisticated.¹

Q. What did the mother broom say to the baby broom?

A. Time to go to sweep.

Q. Where does a general keep his army?

A. In his sleevey

Q.  Did you hear what happened to the Italian chef that died?

A. He pasta -away.

I went to the video store and asked to borrow Batman Forever. They said, “No, you have to bring it back tomorrow.”

A horse walks into the bar and the bartender says, “Hey” and the horse says, “Sure”.

1. http://www.word-detective.com/