One explanation is that the usage derives from the weatherproof outer clothing worn by enthusiasts of offshore radio, who would sometimes visit the ships from which their 'outcast heroes' broadcast during the 1967–76 period. The term was, reportedly, coined by Andy Archer, a disc jockey of the time - presumably as the appearance of these enthusiasts made a collective impression - and later became generalized to mean an obsessive enthusiast of other activities.

The word can be qualified by the area in which the person takes an excessive interest; a "timetabling anorak" would be someone who finds the process of timetabling classes fascinating.

Roy Cropper, a character from the popular British soap opera Coronation Street, is a stereotypical portrayal of an "anorak." Former British Prime Minister John Major, derided by many for perceived dullness, was described by Anthony Seldon as an "obsessive political anorak."

The majority of Anoraks do not realy care about music, the exception being those whose obbsession is a very specific and obscure artist or style of music. Aside from obviously, anoraks, an Anoraks fashion sense is generally meant to be practical rather than stylish; old jeans and walking shoes being stereotypical anorak wear.

Image by me (sorry it's so pixelated, original version was TINY), Info from wikipedia, last paragraph by me.