Truthiness is a word which was popularized and redefined by comedian Stephen Colbert on The Colbert Show in 2005. Under Colbert's definition, truthiness refers to the things one knows to be true, regardless of pesky information like facts and analysis which might provide contradictory information. Truthiness, in other words, is something felt with the gut. The word quickly caught on, with a number of media outlets adding it to their reports, and in 2006, it was named Word of the Year by both the American Dialect Society and Merriam-Websters Dictionary.
While uses of the word date back to the early 1800s, Colbert's definition has become much more widely known, and in all probability, he came up with the word without realizing that it already existed. Reports indicate that Colbert came up with “truthiness” shortly before the episode it aired in, wanting to come up with a particularly ludicrous word for the segment of the show known as The Wørd.
In an interview in which he was asked about truthiness, Colbert explained that he had intended to use the word as a criticism of the constant appeals to emotion used by many American politicians. He also pointed out that facts seemed to matter less and less in the United States, citing this as a disturbing trend. In the segment where the word was introduced, he said that “...we are divided between those who think with their head, and those who know with their heart.”
The Colbert Report may be a satirical show, but its commentary on American culture and politics is often very astute. While truthiness originally emerged as a quick soundbite for a segment on the show, the word quickly took on a life of its own. “Truthiness” has even created word wars, and a memorable standoff between Colbert and the Associated Press, which used the word in a report without crediting Colbert.
Thanks to the widespread popularization of the word, truthiness pops up in all sorts of places, including entirely legitimate articles and commentaries. Some of the usages of its word have deviated from its original meaning, although they capture the spirit of satire and criticism which “truthiness” was meant to imply. Some Colbert fans point out that truthiness is a serious threat in the United States, citing things like the invasion of Iraq on spurious grounds as the consequences of truthiness taken to extreme levels.
A closely related word is “Wikiality,” a portmanteau of “Wikipedia” and “reality,” which is described as a form of truthiness by consensus.