Borrowed from Greenlandic Inuit 'annoraaq' — a hooded sealskin garment that crossed from Arctic survival gear to fashion.
A waterproof hooded jacket; in British slang, a person who is obsessively interested in a niche subject.
From Kalaallisut (Greenlandic Inuit) 'annoraaq' (a hooded waterproof garment made of sealskin), used by the Inuit peoples of Greenland for protection against Arctic weather. The word was adopted into English through contact with Greenlandic and Danish-speaking communities. The British slang sense of 'a boring, obsessive person' (1980s) comes from the stereotype of trainspotters and
In British English, 'anorak' became slang for a boring, obsessive person in the 1980s — derived from the image of trainspotters standing on railway platforms in all weather, always wearing anoraks. It is roughly equivalent to American 'nerd' or 'geek.' This makes 'anorak' one of the few Inuit words