Corn is an English word dating back to Anglo-Saxon times or earlier meaning cereal or grain. It commonly refers, in modern American usage, to Indian corn, that is, maize, but can also refer to wheat, barley, rye and so on.
It was a lover and his lass, With a hey and a ho and a hey, nonny-no, That o’er the green corn field did pass, In spring time ...The second verse goes on
Between the acres of the rye, With a hey and a ho and a hey, nonny-no, These pretty country-folks would lie, In spring time ...indicating the meaning of the corn in this case.
And all countries came into Egypt to Joseph for to buy corn; because that the famine was so sore in all landswhere modern US versions have for example
In fact, all the world came to Joseph to obtain rations of grain, for famine had gripped the whole worldThe early nineteenth century British Corn Laws referred to the importation of wheat.
After the colonization of America, maize was introduced to the English-speaking world, and originally known as Indian corn, a term which was then increasingly often shortened to corn in America, but not in the UK, where the original meanings were retained.