The first known uses of the word “nerd” was in a Dr. Seuss work from 1950(“If I Ran the Zoo”), a 1957 Glasgow, Scotland, “Sunday Mail” column titled ‘ABC for Squares’ and as “nurd” in a 1970 U.S. ‘current slang’ listing. There is debate over how the word evolved and acquired its current meaning. As a definition, I like what I found at UrbanDictionary.com which goes something like this- someone who enjoys what they do and doesn’t conform to what is cool. Usually insulted by “cool kids” who tell them how to live their lives. The wikipedia website contains a varied and in-depth coverage of the subject.
Social ineptness is frequently mentioned when describing nerds.
“geek” also enters into the discussion but I am in the camp that believes you can separate the two based on the early use of “geek” to describe players in Circus Side Show acts. Geeks draw attention to themselves where nerds are withdrawn. For example, people who like to recite entire scenes from certain movies (Blazing Saddle, Monty Python and the Holy Grail, Airplane come to mind) are geeks. Nerds may enjoy those movies (I know I have) but they don’t try to use the dialogue as entertainment at parties or as pick-up lines because their tongues are too easily twisted and they stumble over the words when they try.
I disagree with people who lump nerds and computers together. Not all nerds use computers and not all computer users are nerds. (as he types away on the keyboard without any trace of irony)