The "N" theory is something I've been playing around with in my head for a while now and seeing as someone else has mentioned it I'll elaborate on my thinking.
What if, say these map packs turn out to spell out Runs? "Fear Runs" doesn't make much sense on its own, but consider if we were given a Black Ops 3 next year, and the map packs were to spell out "deep". I personally think this theory holds alot mopre weight than the "Fear Russ" theory, as the forethought to have a zombie "script" thought out from the get go, before they realised that Black ops was going to do so well, so far as having the name of a character before the second game is even at concept stage is a bit much to believe. As fear would have stood alone well with there just being one game, and "runs" is possibly an extended afterthought.