In British slang an anorak is a person who has a very strong interest, perhaps obsessive, in niche subjects. This interest may be unacknowledged or not understood by the general public. The term is sometimes used synonymously with geek or nerd, the Japanese term otaku, albeit referring to different niches.
In 1984 the Observer newspaper used the term as an alternative term for the prototype group interested in detailed trivia, the trainspotters, as members of this group often wore unfashionable coats called anoraks when standing for hours on station platforms or along railway tracks, noting down details of passing trains.
The first use of the phrase to describe an obsessive fan has also been credited to the radio presenter Andy Archer, who used the term in the early 1970s for fans of offshore radio, who would charter boats to come out to sea to visit the radio ships.