In British slang an anorak ( /ˈænəræk/) 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. Although the term is often used synonymously with geek or nerd, the Japanese term otaku or the American term "fanboy/fangirl" are probably closer synonyms.
The most established explanation to the origin of the term, is that it was first used in 1984 by the Observer newspaper, which used it as an alternative term for the prototype group interested in detailed trivia, the trainspotters,[1][2] as members of this group often wore, by then very unfashionable, civilian versions of the USAF N-3B parka with fur-lined hood, which was often called an anorak in the UK, when standing for hours on station platforms or along railroad tracks, noting down details of passing trains.
Civilian versions of the N-3B parka (commonly called snorkel parka, because the hood can be zipped right up leaving only a small tunnel/ snorkel for the wearer to look out of) were extremely popular among youths in the UK in the late 1970s to mid 1980s, and at many schools almost every boy had one. By the second half of the 1980s the parka had become unfashionable, but was still commonly worn among trainspotters, as it was practical for their hobby and as most of them were uninterested in being fashionable. This reinforced the usage of the term further, and it soon became derogatorily used for any group of (mostly) younger people uninterested in their outer appearance and engrossed in activities that other youths found boring, i.e. "geeks" or "nerds".