...is a nonsense word created for the Illuminatus! novel trilogy. In the story, the word FNORD is inserted subliminally throughout the media to induce a subtle sense of unease and paranoia in the populace. It has since become a trope of sorts in video games and interactive media. Developers will quietly insert the word FNORD into their writing (often in invisible text) as an homage to the acid trip in book form that is Illuminatus!.
How many of these people have actually read any of Illuminatus!? That's hard to say. These are not the easiest novels in the world to read, although if you ever have wondered what a psychedelic episode is like but are unwilling to approach a drug dealer, then by all means track down a copy. If nothing else, it should give you some reference point for this and other insider memes favored by indie developers.