How could the Romans use corn? It's American!
Recently the "I, Claudius" series on public television had an episode where Claudius gains the popularity of the masses by building a harbor to bring more corn to Rome. The Encyclopedia Britannica also refers to this. But wasn't corn domesticated in the Americas? And weren't American plants in short supply in B.C. (Before Columbus) Rome? And wouldn't it be fun to embarrass PBS and EB by pointing out that in Rome there was no corn?
There's nothing I'd enjoy more than humiliating the two overrated institutions you mention, but I'm afraid you're the only target in range at the moment. "Corn" comes from the Latin word for grain (granum), and through the ages it's been used indiscriminately for whatever grain happens to predominate in a particular region.
In England, for example, corn is the word the natives apply to wheat. Up country a bit, in Scotland, the locals say "corn" when they mean "oats." Naturally, when our British forebears jumped off the Mayflower and found the welcoming committee brandishing long green stalks with funny yellow things pointing out of them, "corn" was the first word that came to mind, and the name stuck in American English.
"Indian corn," as the plant is called now and then, is a more logical and precise name (at least if you're willing to be tolerant about the "Indian" part). Better yet is "maize," the term used by thinking botanists and by English-speaking peoples outside the Americas, where the word "corn" is already spoken for.
Maize is, of course, a product of the New World. No historical evidence suggests that any European had encountered it before Christopher Columbus landed in Cuba. According to Columbus's journal for that fateful day, November 5, 1492, two Spanish scouts he had sent to explore the interior of the island came back with wild tales of "a sort of grain . . . which was well tasted, baked, dried, and made into flour." The natives, in their Taino dialect, called it mahiz, which Columbus promptly corrupted into maiz or maize.
So, getting back to Claudius, he was really expanding the harbor to accommodate more wheat, thus upping the pasta supply. Claudius would have called it granum, and the BBC scriptwriters' rendering, "corn," becomes confusing when the program is shipped over for American consumption. An even more confusing episode occurs in the Masterpiece Theater debasement of Anna Karenina: two characters are standing in the middle of what is manifestly a wheat field, making casual references to the sea of "corn" that surrounds them. If PBS is going to insist on importing all their blockbusters from England, maybe they ought to consider adding subtitles.