While most people in my internet circles use the word "geek" more often than nerd, it has still lost most negative connotations in my mind. Yet, once again, my mind is not in sync with much of the English speaking world. In fact, one of OED's first descriptors for the word, after "slang," is "derogatory."
Nerd's origin is recent, "uncertain and disputed." It may be from a fictional animal in Dr. Seuss's If I Ran the Zoo, published in 1950. It could also be a euphemism for "turd," although the spelling makes it unlikely (OED). Douglas Harper agrees that Dr. Seuss's book might have played a part in the popularity of nerd. However, he pins its rise in 1951, "probably an alteration of the 1940s slang nert 'stupid or crazy person,' itself an alteration of nut."
Regardless of its origin, nerd has grown to include "socially inept" people, those who are "boringly conventional or studious," and, more recently, "a person who pursues an unfashionable or highly technical interest with obsessive or exclusive dedication" (OED).
That last definition lines up most with my use of the word. Much of the world might still mean nerd as an insult, but that doesn't stop us from using it in a more positive tone. In fact, I'm rather thankful to the name-callers. Without them, those of us with "uncool" interests would have to come up with our own names and adjectives for ourselves. It's much easier to just hijack so-called "derogatory" terms and make them our own.
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“Nerd, n.” OED Online. Oxford University Press, March 2014. Web. 16 April 2014