Narcissism is the personality trait of egotism, often used as a pejorative, denoting vanity, conceit, egotism or simple selfishness. Applied to a social group, it is sometimes used to denote elitism or an indifference to the plight of others.

The name "narcissism" is derived from Greek mythology. Narcissus was a handsome Greek youth who, having never seen his reflection because of a prediction by an Oracle, looked in a pool of water and saw his reflection for the first time. The nymph Echo who had been punished by Hera for gossiping and cursed to forever have the last word. She had seen Narcissus walking through the forest and wanted to talk to him, but because of her curse she wasn't able to speak first. As Narcissus was walking along he got thirsty and stopped to take a drink, it was then he saw his reflection for the first time, not knowing any better he started talking to it. Echo, who had been following him then started repeating the last thing he said back, not knowing about reflections Narcissus thought his reflection was speaking to him. Unable to consummate his love, Narcissus pined away at the pool and changed into the flower that bears his name, the narcissus.

Freud believed that some narcissism is an essential part of all of us from birth. Andrew P. Morrison claims that, in adults, a reasonable amount of healthy narcissism allows the individual's perception of his needs to be balanced in relation to others.

The concept of excessive selfishness has been recognized throughout history. In ancient Greece the concept was understood as hubris. It is only in recent times that it has been defined in psychological terms. In 1898 Havelock Ellis, an English sexologist, used the term "narcissus-like" in reference to excessive masturbation whereby the person becomes his or her own sex object. Otto Rank in 1911 published the first psychoanalytical paper specifically concerned with narcissism linking it to vanity and self-admiration. Sigmund Freud only published a single paper exclusively devoted to narcissism in 1914 called, "On Narcissism: An Introduction." In 1923, Martin Buber published his essay "Ich und Du" (I and Thou) in which he pointed out that our narcissism often leads us to relate to others as objects instead of as equals.

Although most individuals have some narcissistic traits, high levels of narcissism can manifest themselves as a pathological form as Narcissistic Personality Disorder, whereby the patient overestimates his or her abilities and has an excessive need for admiration and affirmation.

Ref: http://en.wikipedia.org/wiki/Narcissism