In chapter 3 of Histories by Herodotus he talks about corn being set alight. How is this possible with corn being native to North America?

To elaborate just a bit on the older answer if anyone's curious: "corn" or "korn" has been part of the English language for longer than there has been a distinct English language. Some slight variation of the same word, with the same pronunciation even, appears in almost every documented Germanic language. For example, in Gothic, which is about as far from English as you can get and still be Germanic, it is kaurn (𐌺𐌰𐌿𐍂𐌽). As u/jschooltiger noted way back when, historically "corn" was just used to mean "grain," usually, but not always, wheat. It doesn't even change that much when you get into reconstructed proto-Germanic, where the word is usually rendered as *kurna.

Specifying maize as "corn" was an American phenomenon up to the 20th Century, and really the latter half of the 20th Century. However, the reason why English has two words that basically just mean "any and all wheat-and-maize-like-food-crops" is also an interesting twist of linguistic history. "Grain" entered Middle English from Latin via French. Like many French food words, there was a bit of class distinction between who used "corn" (poor English speakers) and "grain" (well-off French speakers). Likewise, along with many other Latinate words, "grain" gained favor with the English literati during the Renaissance and became more common and "ingrained" in the language.

But the Latin root word granum, meaning both "kernel of grain" and "seed," is actually cognate with "corn" if you go all the way back up to reconstructed Proto-Indo-European. Usually written as *g'rhnom, that word also meant something like "grain, kernel, or seed," and seems to have derived from a word that meant "to grow." By extension, that also makes "corn" cognate with "geriatric" from Greek geros (γῆρας), meaning old age, and maybe more interestingly: cognate with the word "Greek" itself, depending on the etymology you accept. One theory holds that "Greek" derives from the city of Graia, literally meaning grey (also a cognate from this same root), possibly because of how hair/fur turns grey with age.