Mythical Unicorns
The mythical unicorn likely derives from travelers from Africa or Asia to Europe trying to describe a rhinoceros (there are Asian rhinos in India, Nepal, and Indonesia). When you consider that ancient Greek depictions of lions sometimes looked more like dogs and that the word hippopotamus comes from Greek words meaning “river horse,” it’s easy to see how a Greek traveler would describe a rhino as a one-horned horse.
There’s linguistic evidence for this idea. Four hundred years ago, it was believed that there were two types of rhinos. Ones with two horns were called “rhinoceros,” and ones with a single horn were called “unicorns.” So the word unicorn was used to describe both real rhinos and the mythical one-horned horse. It wasn’t until zoology advanced as a science that ‘unicorn’ came to refer purely to the mythical creature. There are still remnants of the original usage, though. The genus of scientific name for Asian rhinos (which have one horn) is ‘unicornus.’