corn

Corn comes from Old English corn, from Proto-West Germanic *korn, from Proto-Germanic *kurną, tracing back to Proto-Indo-European *ǵr̥h₂nóm, meaning 'grain' or 'worn-down' — related to the idea of maturing or growing old.

For most of its history, corn simply meant grain in general — wheat, barley, rye, whatever the local crop was. In 18th-century North America, 'Indian corn' got shortened to just 'corn,' narrowing the word to mean maize specifically.

It's a doublet of grain, gram, granum, and grao, and cognate with Dutch koren, German Korn, and Latin grānum — all ultimately grains of the same root. The adjective corny and the modern slang use of corn as a rhyming stand-in for porn are separate, later developments.