“Otaku” as a word to describe the subculture of fans depicted in Otaku no Video has had a complex history ever since the emergence of that subculture in the late 1970's and early 1980's.
Literally, “otaku” is a formal, highly polite way of saying “you” or “your house”. Accounts vary of how it became associated with fan subculture, but the general consensus is that science fiction fans used it as an idiosyncratic way of addressing each other, possibly mimicking the polite speech of housewives in Osaka (where the members of Gainax came from) and/or adopting an exaggerated formality when interacting with other fans at otaku gatherings and events.
As such, videophiles in the 1980’s used the word to refer to “your video” (“otaku no video”). They used the term enough that they were eventually referred to by the public as the “Otaku-zoku” (“Otaku Tribe”), and later just “otaku”. The word took on the rough meaning of “maniac” or “hardcore fan”. Thus, the title Otaku no Video has another meaning: “Otaku’s Video” or Maniac’s Video“.
Unfortunately, in the late 1980's, many Japanese heard the term “otaku” used in conjunction with a crime committed by a man named Miyazaki Tsutomu. Miyazaki was a serial killer who preyed on children. Photographs of his two-room home taken after his arrest showed that he had a huge collection of videotapes, which allegedly contained anime, slasher, and pornographic films. Because of this, the Japanese media depicted him as an otaku, triggering a moral panic against otaku culture in general.
The term “otaku” retained a gruesome connotation for some time, but the word eventually lost much of this grotesque stigma, perhaps helped by the release of Otaku no Video and the global spread and evolution of otaku culture.
In Japan, it is possible to be an otaku of just about any hobby, niche, or genre. This is illustrated both in the “Portrait of an Otaku” interview segments, as well as in the quirks and specialties of the characters in the main feature. In Japan, there was a TV quiz show called Cult Q, which was essentially a game show for otaku of all stripes. All areas of expertise were on the table, from tropical fish to ingredient labels of over-the-counter drugs!
Because Japanese animation has been such a significant cultural export to the rest of the world, the term “otaku” in the West has been associated most strongly with anime fan subculture.