The translation into English "corn" doesn't refer to maize. It's unidiomatic in modern English but Gutenberg only has copyright-free translations, and this one is from the 19th century.

edit: The word in the source text is frux (fruge)

https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext...

https://en.wiktionary.org/wiki/frux#Latin

"Corn" traditionally just meant grain. "Corn" meaning maize is an abbreviation of "Indian corn", i.e. the grain used by Native Americans.

Corn still means wheat, rye, etc. in British English. Maize is sweetcorn.

Sweetcorn is a specific maize meant for human consumption, distinct from popcorn or feed corn (which is also used for ethanol production, becoming "distillers grains" that are also fed to livestock).