http://en.wikipedia.org/wiki/Truthiness

… the term is actually included in the Oxford English Dictionary as a derived form of “truthy.” The entry is marked as “rare or dialectal,” with a single citation of “truthiness” dated to 1824 (though it has been posited that the citation actually dates to 1837, with an earlier citation dating to 1832). As such, Colbert seems to have unknowingly reinvented the word, though he also invented a new, ironic meaning for it, where the original meaning was akin to “truthfulness.” This distinction is consistent with the announcement by the American Dialect Society, in that it credits “truthiness” as “Recently popularized on the Colbert Report” rather than “invented.”

I am amused that this article is plagued by vandalism.