The green-eyed monster is an idiomatic expression in the English language which is used to describe an overwhelming sense of jealousy. By using this phrase, jealousy is personified as a beast, indicating just how destructive it can be as an emotion. This phrase was first used by William Shakespeare, who used it in two of his most famous works, "The Merchant Of Venice" and "Othello." It is likely that jealousy is labeled a green-eyed monster because of the association of the color green with sickness or things that cause illness.
Many people who speak English add some color and expressiveness to their daily speech by using idioms. Idioms are short phrases which tend to change meanings over time until they mean the same thing to most people in a culture. These accepted meanings may be quite different than both the origins of the phrase and the literal definitions of the words they include. Some of these phrases can trace their origins back to the famed British playwright William Shakespeare, who coined the phrase green-eyed monster.
Shakespeare used the phrase "green-eyed jealousy" in his play "The Merchant Of Venice", and later called compared jealousy to a cat, a "green-eyed monster," in his tragedy "Othello." It's likely that the idiom has its origins from some combination of these two uses. In addition, the color green has long been associated with unhealthiness. People who are sick often have a greenish color, and certain foods cause illness when they are green.
This idiom has originated from all of these sources and is used so often in the English language that it borders on being considered a cliche. The power of the phrase comes from the associations people have with monsters, who are considered scary and destructive creatures. As such, combining the unhealthy associations with green with the scary descriptions of monsters makes green-eyed monster a seriously lethal description for an emotion.
When someone uses this phrase, he or she is essentially personifying the emotion of jealousy. This emotion can be especially harmful, not only to those who are envious of other people, but also to those who are being envied. It also causes people to act in ways that they might not otherwise consider. That is why the description is so evocative of jealousy and all the damage it can do. As an example, someone might say, "I couldn't stop thinking about my former girlfriend with her new guy; I guess the green-eyed monster got me."