“corn” (or cō̆rn) meant any small seed or grain, like a grain of sand, salt, or cereal, deriving from a Proto-Germanic word for “small seed” (kurnam) and ultimately PIE ǵrh₂nóm. It was a general term for local cereal crops, so in England it meant wheat or barley, in Scotland oats, and later, when Europeans met maize in the Americas, they called it “corn” because it was the local grain.

Thats how corned beef got named corns of salt.