"Nerd" Defined

Nerd (adjective: nerdy) is a descriptive term, often used pejoratively, indicating that a person is overly intellectual, obsessive, or socially impaired. They may spend inordinate amounts of time on unpopular, obscure, or non-mainstream activities, which are generally either highly technical or relating to topics of fiction or fantasy, to the exclusion of more mainstream activities. Additionally, many nerds are described as being shy, quirky, and unattractive, and may have difficulty participating in, or even following, sports. Though originally derogatory, "Nerd" is a stereotypical term, but as with other pejoratives, it has been reclaimed and redefined by some as a term of pride and group identity. 

Etymology

The first documented appearance of the word "nerd" is as the name of a creature in Dr. Seuss’s book If I Ran the Zoo (1950), in which the narrator Gerald McGrew claims that he would collect "a Nerkle, a Nerd, and a Seersucker too" for his imaginary zoo.  The slang meaning of the term dates back to 1951, when Newsweek magazine reported on its popular use as a synonym for "drip" or "square" in Detroit, Michigan.  By the early 1960s, usage of the term had spread throughout the United States, and even as far as Scotland At some point, the word took on connotations of bookishness and social ineptitude.

An alternate spelling, as nurd, also began to appear in the mid-1960s or early 1970s. Author Philip K. Dick claimed to have coined this spelling in 1973, but its first recorded use appeared in a 1965 student publication at Rensselaer Polytechnic Institute.  Oral tradition there holds that the word is derived from "knurd" ("drunk" spelled backwards), which was used to describe people who studied rather than partied. The term nurd was in use at the Massachusetts Institute of Technology as early as 1971.

The Online Etymology Dictionary speculates that the word is an alteration of the 1940s term nert (meaning "stupid or crazy person"), which is itself an alteration of "nut".

The term was popularized in the 1970s by its heavy use in the sitcom Happy Days.

“Nerdy” Interests

• Intellectual, academic, or technical hobbies, activities, and pursuits, especially topics related to science, mathematics, engineering, linguistics, history and technology.
• Hobbies, games, and activities that are described as obsessive and "immature", such as trading cards, comic books, fantasy and science fiction novels, television programs, and video games.
• Interest in the fine arts, non-mainstream music such as classical, techno, or folk music, hobbies (i.e., collecting), or other "obscure" interests.
• Heavy obsession with a topic that would otherwise be mainstream (such as a popular TV show or a sport).

http://en.wikipedia.org/wiki/Nerd