N Polyamory, also called a "Fluid Chain", is a type of quad polyamorous relationship structure. It is a relationship involving four people, generally two preestablished couples, where one member of one couple is also involved with one member of the other couple. For example: A and B are dating. C and D are dating. B and C are also dating. However, C is not dating A, and B is not dating D. A and D are also not dating.
It is unknown when the term was coined however it has been around since 2016.
The flag was coined by Deviantart user NonMonoPrideFlags on January 15th of 2016. It has no confirmed meaning.