Otaku can be Japanese or foreign. It basically means "nerd", and is usually associated with people obsessed with manga and anime.

I think the word you're thinking of is weaboo, which is a derogatory term for Japanophiles.

I wouldn't say that Japan was "revered", but Japonism was a very influential style in art, decoration and the like through the 19th century and some time afterwards. As you might know, the country had an isolationist policy from the 17th century up until 1854, when Commodore Matthew Perry forced the shogun to open the ports to international commerce. Commerce was never completely cut and some pieces of Japanese pottery and art reached Europe before that time thanks to Dutch ships, but it's at this time when it becomes something of a craze. Prints, clothes, and other things are imported and start being imitated. With the opening of the ports, Japanese artists are free to travel abroad and, some years later, troupes like the ex-geisha Sadayako's (known internationally as Sada Yacco) triumph in America and Europe, inspiring new articles of fashion like kimonos, etc. So we could say that the interest in Japan has been there for a long time, even if not in a constant manner.

Edit: word.

That's not what otaku means.