corn (n.2)

"hardening or thickening of skin," early 15c., corne, from Old French corne (13c.) "horn (of an animal)," later "a corn on the foot," from Latin cornu "horn of an animal," from PIE root *ker- (1) "horn; head."

Latin cornu was used of many things similar in substance or form to the horns of animals and of projecting extremities or points: It could mean "a wart, a branch of a river, a tongue of land, the end of a bow or sail-yard, the peak of a mountain, a bugle, a wing of an army," or "the stiff hair of the Germans."

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