talk through one's hat

Attested from the late 19th century in the United States in the sense of “bluff”; the sense “speak without authority or knowledge” developed later. Although some people speculate a connection to a former requirement that British Members of Parliament wear hats, the connection is implausible.

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talk through one's hat (third-person singular simple present talks through one's hat, present participle talking through one's hat, simple past and past participle talked through one's hat)

1. (idiomatic) To speak lacking expertise, authority, or knowledge; to invent or fabricate facts.

   Synonym: talk through one's ass

   • c. 1900, Gilbert Parker, At The Sign Of The Eagle:

     "Mr. Pride said to me a moment ago that they spoke better English in Boston than any other place in the world."
     "Did he, though, Lady Lawless? That's good. Well, I guess he was only talking through his hat."

2. (idiomatic) To assert something as true or valid; to bluff.
   • 1905, “The Norsk Nightingale”, in Popular Mechanics‎, page 478:

     No, sir, she yust standing pat, / And vonce more she tal her father, / “Yu ban talking tru yure hat!”

   • 1922, P. G. Wodehouse, chapter 14, in Right Ho, Jeeves:

     He's conceited and opinionative and argues all the time, even when he knows perfectly well that he's talking through his hat.

• nonsense
• BS

• “talk through one's hat”, in OneLook Dictionary Search.
• Gary Martin (1997–) “Talk through one's hat”, in The Phrase Finder.