Hello AskHistorians!

Reading Caesar's Commentaries, I notice that we come across plenty of references to campaign life -- and in particular, the supply of the camp, the state of the soldiers' lives, and their eating habits. Most specifically, Caesar mentions dozens of times soldiers having their 'corn' or eating their 'corn.'

Now, as per the AskHistorians FAQ and my own research, I believe I understand the Roman legionaries were likely to be eating (amongst many other things of a balanced diet) wheat -- whether hardtack ground into flour, or puls porridge, or whatever.

I also know that what I think of as corn -- maize -- is a New World crop, and thus obviously unavailable to the Romans.

So my question is not what did the Romans eat on campaign -- but rather why all of the translations seem to go for 'corn' instead of something like 'grain' or 'wheat' or 'millet'. I suppose the question is a little bit about the etymology of 'corn', but it's also about the shift in our understanding of staple grains and crops. For example, the Northern Italians are famous for (amongst other things) their polenta, which they say is a food and recipe basically unchanged since Roman times -- but these days, they almost ubiquitously use corn maize in their polenta.

So what gives? Has there been a language shift on what 'corn' means ever since the Columbian Exchange? Am I wrong in thinking the Romans had no access to maize? Is someone bizarrely mistranslating 'wheat' into corn? What is the grain that Caesar is calling 'corn' and why is it being called that?!

As ever, thanks AskHistorians; you're the best.