"the brain," 1610s, from Latin cerebrum "the brain" (also "the understanding"), from PIE *keres-, from root *ker- (1) "horn; head."
"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."
zodiac sign represented as a goat, or half-goat half-fish, late Old English, from Latin Capricornus, literally "horned like a goat," from caper (genitive capri) "goat" (see cab) + cornu "horn" (from PIE root *ker- (1) "horn; head"). A loan-translation of Greek Aigokherōs, the name of the constellation. Extended 1894 to persons born under the sign.
piercing appendages in the proboscis of scorpions and spiders, 1831, plural of Modern Latin chelicera, from Greek khēlē "crab claw, talon, pincers; cloven hoof of cattle, horse's hoof," metaphorically "surgical forceps, hooked needle, crochet needle, notch of an arrow," a word of uncertain origin with no agreement on ulterior connections (according to Watkins, related to keras "horn," from PIE root *ker- (1) "horn; head"). Earlier chelicer (1835), from French chélicère.
"hind-brain of a vertebrate animal," 1560s, from Latin cerebellum "a small brain," diminutive of cerebrum "the brain" (also "the understanding"), from PIE *keres-, from root *ker- (1) "horn; head." Related: Cerebellar.