Meaning

noun an imaginary creature represented as a white horse with a long horn growing from its forehead

originFrom Middle English unicorne, unikorn, from Anglo-Norman unicorne, Old French unicorne, and their source, Latin ūnicornis, from ūnus (“one”) + cornū (“horn”). Displaced native Old English ānhorn, itself a calque. Other senses from either rarity (e.g., possessing multiple skills) or by physical resemblance to having a horn (e.g., howitzer). The finance sense was coined by American investor Aileen…

Etymology from Wiktionary, CC BY-SA 3.0