Fenris was a planet on which the Fenris Rangers were based. By 2399, the planet was said to be going through tough times.
Seven of Nine and Bjayzl first met on Fenris, where the latter was posing as someone who wanted to help. (PIC: "Stardust City Rag")
Fenris shares its name with the Fenris Wolf, also called Fenrir, of Norse mythology. Fenrir is chained by the gods, but fated to break free at the final battle of Ragnarok, where he will slay Odin before being killed in revenge by Odin's son. Coincidentally, a ship named for Odin appeared in TNG: "Angel One".