In a group, a taboo is something that the group thinks is bad and should not be done. Sometimes even talking about taboos is taboo.  Some actions that are thought of as taboo may also be against the law.  Breaking the taboo may be punished hard by those states. Breaking other taboos can result in feeling embarrassed, or ashamed. Breaking a taboo is sometimes seen as rude.

The English word is traced back to Tongan tapu[1][2] or the Fijian tabu.[3] These words usually mean "not allowed", or "forbidden".[3] In its current use in Tonga, the word tapu also means "sacred" or "holy", in the sense of being restricted or protected by custom or by law.  For example, the main island in the Kingdom of Tonga, where the capital Nuku'alofa is located and most of the population resides, is called "Tongatapu".

The use of the word taboo drawn from tapu.  "Tapu" means "not allowed".  It dates back to 1777 and an English explorer, Captain James Cook, went to a place he named "the Friendly Islands" (now Tonga). Writing about the Tongans, he wrote:

—James Cook, 1777

Some Solomon Islanders say that their languages have a word tabu (said like "ta-boo") that means holy.  It refers to places in the bush where holy spirits live.  Those areas should not be disturbed unless a ceremony or ritual is taking place.  As taboo, they are places that should not be touched.

Taboos can include:

Some taboos are because a religious, legal or social authority did something, over and over. Taboos can be talked about or joked about, outside "polite society". Comedy and satire such as South Park, The Simpsons or Beavis and Butthead frequently do this.

There have been two main groups of explanations why taboos exist:

One suggestion is that taboos are the result of history and certain cultural experiences (which is called Anthropolcial approach). Steven Pinker suggests that taboos have developed culturally from more basic instincts. For taboos regarding the dead, he proposes that the human brain may have developed a hard-wired repulsion to many carriers of disease – an "intuitive microbiology". Only with the modern development of scientific microbiology have humans been able to rationalize these taboos. Pinker suggests similar explanations for the incest taboo and other things that cause the reflex emotion of disgust.

The other proposal is that taboos are the result of unconscious phenomena that are passed on (and this is called Psychoanalytical approach). Sigmund Freud provided an analysis of taboo behaviours.  He highlighted strong subconscious motivations behind such prohibitions.  In this system, described in his collection of essays Totem and Taboo, Freud says there is a link between forbidden behaviours and the sanctification of objects to certain kinship groups. Freud also states that the only two "universal" taboos are that of incest and patricide, which formed the eventual basis of modern society.

German psychologist Wilhelm Wundt explains that taboos were originally nothing other than an objectified  fear of a "demonic" power which was believed to lie hidden in a tabooed object.[4] Sigmund Freud believes this to be a superficial explanation having nothing to do with the true origins of taboos. He claims that many similarities between taboo-holders and obsessive neurotics point to "a psychological condition that prevails in the unconscious".[5] Freud believes this "unconsciousness" is central to understanding the history of taboos. He then reconstructs the history of taboo based on the model of obsessional prohibitions as follows:

And so, "Anyone who has violated a taboo becomes taboo himself because he possesses the dangerous quality of tempting others to follow his example."[7]