Some speculate that bloviate derives from adding a faux-Latin ending to the verb 'to blow' or boast, following a 19th-century fad of adding Latin-like affixes to ordinary words. However, others like William Safire claim that 'bloviate' comes from combining the words 'blow-hard' and 'deviation.'
Although 'bloviate' is listed in slang dictionaries as far back as the 19th century, the term was popularized by President Warren G. Harding in the 1920s. Famed for his poor English usage, Harding often used the word to describe his long, winding speaking style. The term dropped from popular usage following his presidency but was resurrected in the 1960s when it was sometimes used in reference to Harding.
The term is used frequently by Fox News commentator, Bill O'Reilly whose show, The O'Reilly Factor concludes with requests for email. The request for feedback, sometimes includes: "Please do not bloviate, [that's] my job."
'Bloviating' has taken on new life in the blogosphere, used derisively to identify and otherwise chide the most pompous of contributors to message boards and forums.