Provenance — where it came from
お宅 (otaku) is an old, polite word. It literally means “your home,” and by extension, a formal “you” — the kind of distant politeness you use with a neighbor you barely know.
In the early 1980s, at comic conventions, hardcore fans of anime and manga addressed each other with exactly this word. Not “hey, you” but “and your home?” — formal, careful, a little awkward. In 1983, the columnist Akio Nakamori noticed this habit and named the whole tribe after it: otaku. He did not mean it kindly. For years the word was an insult — someone too deep in a hobby to face the world.
Then the hobby conquered the world. As anime and manga spread abroad, the word traveled with them, and the sting wore off along the way. Today “otaku” appears in English dictionaries, and people around the world call themselves otaku with plain pride. Few of them know they are saying “your home.”
Field notes — how it’s used
鉄道オタク
tetsudō otaku
“a railway otaku.” Any deep hobby can take the word.