In The Illuminatus! Trilogy, the interjection "fnord" is given hypnotic power over the unenlightened. Under the Illuminati program, children in grade school are taught to be unable to consciously see the word "fnord". For the rest of their lives, every appearance of the word subconsciously generates a feeling of uneasiness and confusion, and prevents rational consideration of the subject. This results in a perpetual low-grade state of fear in the populace. The Government acts on the premise that a fearful populace keeps them in power.
In the Shea/Wilson construct, fnords are scattered liberally in the text of newspapers and magazines, causing fear and anxiety in those following current events. However, there are no fnords in the advertisements, encouraging a consumerist society. It is implied in the books that fnord is not the actual word used for this task, but merely a substitute, since most readers would be unable to see the actual word.
To see the fnords means to be unaffected by the supposed hypnotic power of the word or, more loosely, of other fighting words. A more common expression of the concept would be "to read between the lines." The phrase "I have seen the fnords" was famously graffitied on a railway bridge (known locally as Anarchy Bridge) between Earlsdon and Coventry (U.K.) city centre throughout the 1980s and 1990s, until the bridge was upgraded. The bridge and the phrase were mentioned in the novel A Touch of Love by Jonathan Coe.
"Fnord" is a popular word with followers of Discordianism. Its use in the Principia Discordia predated the Illuminatus! trilogy by several years. It is often used in Usenet and other computer circles to indicate a random or surreal sentence; coercive subtext, or anything jarringly out of context (intentionally or not), can be labelled "fnord".