early 13c., from Old French unicorne, from Late Latin unicornus (Vulgate), from noun use of Latin unicornis (adj.) "having one horn," from uni- "one" (from PIE root *oi-no- "one, unique") + cornus "horn" (from PIE root *ker- (1) "horn; head").
The Late Latin word translates Greek monoceros, itself rendering Hebrew re'em (Deuteronomy xxxiii.17 and elsewhere), which probably was a kind of wild ox. According to Pliny, a creature with a horse's body, deer's head, elephant's feet, lion's tail, and one black horn two cubits long projecting from its forehead. Compare German Einhorn, Welsh ungorn, Breton uncorn, Old Church Slavonic ino-rogu. Old English used anhorn as a loan-translation of Latin unicornis.
"brass musical instrument," mid-14c., abbreviation of buglehorn "musical horn, hunting horn" (c. 1300), from Old French bugle "(musical) horn," also "wild ox, buffalo," from Latin buculus "heifer, young ox," diminutive of bos "ox, cow" (from PIE root *gwou- "ox, bull, cow"). Middle English also had the word in the "buffalo" sense and it survived in dialect with meaning "young bull." Modern French bugle is a 19c. borrowing from English.
1927, imitative of automobile horns (originally of the sound of a certain type of automobile horn, one among several in the years after the klaxon horn was brought into use c. 1910). Used as a noun and verb by 1929. Related: Beeped; beeping.
"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."
"the brain," 1610s, from Latin cerebrum "the brain" (also "the understanding"), from PIE *keres-, from root *ker- (1) "horn; head."
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.
"loud warning horn," 1908, originally on automobiles, said to have been named for the company that sold them (The Klaxon Company; distributor for Lovell-McConnell Manufacturing Co., Newark, New Jersey), but probably the company was named for the horn, from a made-up word likely based on Greek klazein "to roar," which is cognate with Latin clangere "to resound" (compare clang).
slangy salutation current in Britain c. 1907-1923, said by Partridge to be in imitation of bicycle horn noise.
"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.