Otaku is a loan word from Japanese. The original definition meant “a young person who is obsessed with computers or particular aspects of popular culture to the detriment of their social skills.” It’s derived from the Japanese word for “house” suggesting that an otaku was someone who never left the house because of that social awkwardness.
Patrick Macias, editor of Otaku USA magazine, recently summed up the word’s history this way:
The word “otaku” was kind of disreputable in Japan, where it had negative connotations, but lots of American fans were increasingly comfortable using it as sort of a badge of honor; labeling themselves as passionate fans of Japanese pop culture. Most “normal” people didn’t know what the word “otaku” meant at all, and that was fine.
Because there was no social stigma attached to the term in the US, American audiences were able to adjust the definition somewhat so that it meant something more positive, focusing on the passion of being a fan and largely dropping the idea of never leaving your house.
That’s certainly not the only fan-related word that’s had its meaning altered over the years. “Geek” and “nerd” have decidedly less harsh connotations now than they did a few decades ago. In scanning through my copy of Fancyclopedia II from 1959, in fact, many of the terms listed there are no longer even used: “Auslan”, “faaaaan”, “fanne”, and “slan” to name a few.
None of this surprising in that the terminology used within fandom is a language and, as with any language, it will be modified over time. Sometimes through a shift in cultural sensibilities, sometimes via necessity thanks to advances in technology, sometimes by being thrown into the vernacular wholecloth in a work of fiction. (Interesting side note: “nerd” was of the latter type, being created by Dr. Seuss to fit the rhyme scheme in his 1950 book, If I Ran the Zoo.)
Because language is fluid, then, what we’ve been seeing more and more of are people reclaiming terms that were once thrust upon them. Whereas it was once shameful to be called an otaku or geek or nerd, the recipients of those labels found that it was easier to accept the identification and then change what it meant than to argue against it. Rather than shy away or deny the label when it was used against them, they would heartily accept it. “Yes, I am a geek! What of it?”
Changing those definitions doesn’t happen overnight, of course, and a single person alone generally can’t do it by themselves. But as individuals get together and connect with one another—the whole point of fandom after all—they can collectively move the needle on what labels mean and how they’re used.