fanon n. the body of widely accepted fan-created embellishments of a fictional universe, storyline, or character. Editorial Note: Thanks to Ruth Czirr for suggesting fanon as an entry. Etymological Note: fan + ca(n)on. The person quoted in the first 1998 citation has not been verified as the creator of the term fanon. (source: Double-Tongued Dictionary)
Further reading
Mark in Bismarck, North Dakota, spent years as a sailor, and wonders about the term sea painter, meaning “a rope attached to a lifeboat.” Why painter? The word may derive from Middle French pendeur meaning “a kind of rope that...
A resident of Michigan’s scenic Beaver Island shares the term, boodling, which the locals use to denote the social activity of leisurely wandering the island, often with cold fermented beverages. There have been various proposed etymologies...
I find it highly appropriate that four of the five examples used are from four of the largest ‘fanon’ universes: Star Trek, The Sentinel, Harry Potter, and Stargate.