Title: Unicorn Trend
Content:  The unicorn has had an aesthetic and commercial value for centuries. The first written reference to this kind of animals dates back to the fourth century BCE. Later on, they became popular folklore figure, symbols of chastity and purity as they were attracted by the naked breasts of virginal women. Since the ancient Greeks, the unicorn was pictured in the mythology as an elegant beast similar to a white horse with a long and spiraling horn projecting from its forehead. The unicorn briefly appears even in the Old Testament of the Bible under the name of re’em (also reem, Hebrew: רְאֵם), making its way in the Western art and culture during the Medieval and then the Renaissance Age. Over time the unicorn was re-imagined as a toy, characterized by pastel bright colors and sparkly eyes that were popular among young girls during the 1980s.
Title: Unicorn horn
Content:  Marah, so that the good animals could drink. Symbolically, the snake that poisons the water is the devil and the unicorn represents Christ the Redeemer. The origin of this legend seems Indian, and Greek texts report that Indian nobles drank out of unicorn horns to protect themselves from diseases and poisons. The unicorn is most often represented beside a river, lake or fountain, while animals wait for him to finish his work before drinking. This scene is common in the art of the 16th and 17th centuries. Studies and translations of these drawings and stories popularized the belief that the power of the animal came from its horn, which could neutralize the poison as soon as the liquid or solid touched the alicorn piece.
Title: W. Franklin Dove
Content:  The horn of the unicorn dates back all the way to ancient times where they were sought after by kings and queens because they were believed to have magical powers as an antidote against poisons. The typical description in the mythology of a unicorn would have the head and neck and the fine-boned, graceful legs of the horse; the beard and divided hooves of the Capridae; (part of the Artiodactyla family) the tail of the oryx; and a single spike spiraling from the forehead. The artificial production of unicorns has been suggested a number of times in the past. François Levaillant, 1776, in his "Travels to Africa," describes a process of contriving the horns of an ox. During more 
Title: Unicorn
Content:  heal sickness. In medieval and Renaissance times, the tusk of the narwhal was sometimes sold as a unicorn horn. A bovine type of unicorn is thought by some scholars to have been depicted in seals of the Bronze Age Indus Valley Civilization, the interpretation remaining controversial. An equine form of the unicorn was mentioned by the ancient Greeks in accounts of natural history by various writers, including Ctesias, Strabo, Pliny the Younger, Aelian and Cosmas Indicopleustes. The Bible also describes an animal, the re'em, which some translations render as unicorn. The unicorn continues to hold a place in popular culture. It is often used as a symbol of fantasy or rarity.
Title: Unicorn
Content:   Medieval knowledge of the fabulous beast stemmed from biblical and ancient sources, and the creature was variously represented as a kind of wild ass, goat, or horse. The predecessor of the medieval bestiary, compiled in Late Antiquity and known as Physiologus (Φυσιολόγος), popularized an elaborate allegory in which a unicorn, trapped by a maiden (representing the Virgin Mary), stood for the Incarnation. As soon as the unicorn sees her, it lays its head on her lap and falls asleep. This became a basic emblematic tag that underlies medieval notions of the unicorn, justifying its appearance in both secular and religious art. The unicorn is often shown hunted, raising parallels both with vulnerable 
Title: Unicorn
Content:  animals with two horns, one hiding the other, is disproved by a (much smaller) number of small terracotta unicorns, probably toys, and the profile depictions of bulls, where both horns are clearly shown. It is thought that the unicorn was the symbol of a powerful "clan or merchant community", but may also have had some religious significance. In South Asia the unicorn is only seen during the IVC period — it disappears in South Asian art ever since. Jonathan Mark Kenoyer notes the IVC unicorn to not have any "direct connection" with later unicorn motifs observed in other parts of world; nonetheless it remains possible that the IVC unicorn had contributed to later myths of fantastical one-horned creatures in West Asia.
Title: Unicorn
Content:  The unicorn is a legendary creature that has been described since antiquity as a beast with a single large, pointed, spiraling horn projecting from its forehead. In European literature and art, the unicorn has for the last thousand years or so been depicted as a white horse-like or goat-like animal with a long straight horn with spiralling grooves, cloven hooves, and sometimes a goat's beard. In the Middle Ages and Renaissance, it was commonly described as an extremely wild woodland creature, a symbol of purity and grace, which could be captured only by a virgin. In the encyclopedias, its horn was said to have the power to render poisoned water potable and 
Title: Unicorn Trend
Content:  The physical perception of the unicorn has evolved during the years from a white, pure and elegant horse (as portrayed for example in the film Harry Potter and the Philosopher's Stone) to the sparkly and pink creatures of the cartoon TV series My Little Pony, becoming a trendy cultural phenomenon.
Title: Unicorn
Content:  In heraldry, a unicorn is often depicted as a horse with a goat's cloven hooves and beard, a lion's tail, and a slender, spiral horn on its forehead (non-equine attributes may be replaced with equine ones, as can be seen from the following gallery). Whether because it was an emblem of the Incarnation or of the fearsome animal passions of raw nature, the unicorn was not widely used in early heraldry, but became popular from the 15th century. Though sometimes shown collared and chained, which may be taken as an indication that it has been tamed or tempered, it is more usually shown collared with a broken chain attached, showing that it has broken free from its bondage.
Title: Unico
Content:  Originating from the Sanrio Lyrica magazine that ran from 1976 to 1979, the story is about an innocent young (boy) unicorn who possessed a special ability to bring happiness to anyone near him. This magical unicorn concept was naturally aimed at younger audiences, however it grew into larger popularity and is recognized today as a classic retro anime. The story began in ancient Greece with a young mortal girl named Psyche. She was the first friend to Unico, who was apparently so beautiful that the goddess Venus became jealous. The goddess attributes Psyche's beauty to her happiness and decides to remove the magical creature. A series of trickery 

Question: where did the idea of a unicorn come from?
Answer: Greek writers of natural history.