Where does 'talking through your hat' come from?
I've looked it up on phrases.org.uk, which gives the following quote as the first usage:
This began life in the USA, in the late 19th century, with a slightly different meaning from the present one. It then meant to bluster. Farmer and Henley Slang and Its Analogues, 1888:
"Dis is only a bluff dey're makin' - see! Dey're talkin' tru dere hats"
It then gives filibustering in Parliament as a possible link, but I find it hard to connect British politics with American slang used by farmers:
Having made a point of order and while wearing a top hat, an MP couldn't be interrupted and could continue talking for as long as he/she wished.
But agrees that this is unlikely:
Unfortunately, although the link is plausible, I can't find any documentary evidence that links this practice with talking through one's hat. It also seems unlikely that the arcane practices of top-hatted Victorian gentlemen in the UK parliament would have crossed the Atlantic. Much more likely that the phrase originated in the USA and the meaning changed slightly over time.
Is there any better explanation of the origins in America of this phrase?
The earliest use of 'talking through a hat' (and variants) that I found was a prosaic, straightforward simile in the 1864 novel Clara Vaughan, by R.D. Blackmore:
I hear a gruff voice as if it came through a hat.
The next use I found, in the 1879 Decoration Day, an oration at the Academy of Music, New York, Chauncy Depew credits his use of "talking through his hat" to "the slang phrase of my Bowery friends":
After reading all the speeches, some good, some indifferent, some bad and some incomprehensible, except on the theory best expressed by the slang phrase of my Bowery friends that the orator was "talking through his hat"....
So Depew's use of the phrase was to make sense of nonsense. That comports with the contemporary meaning:
to talk about something without understanding what you are talking about
Depew's sense, however, may intimate what appears to have been the more common early meaning of the slang phrase, a sense which is perhaps closer to the literal. That meaning found expression in another early print use:
The very latest remark about the young man who has corralled everything from beer to champagne the nght before and gets around in the morning morose and silent is that "he is talking through his hat." It is said that this is quite as expressive as anything he could say.
The Sun, New York, NY, 11 Nov 1886 (fourth column, toward bottom).
As described, the slang phrase evokes the mumbling, fragmented speech of a drunk or person suffering from a severe hangover, speech that sounds much as might be heard from somebody actually talking through a hat.
In light of this early, more literal meaning, the earlier (at least as early as the 1820s) 'in his hat', a phrase said to be Irish in origin and signifying "drunk" (see also the British slang sense of 'elevated', that is, "intoxicated"), should be mentioned as at least a possible influence on the development of the contemporary meaning of 'talking through his hat'.
British uses of 'talking through his hat', which as far as can be determined (by me, who else) first appeared in the 1890s, seem to be sponsored by the American, as witnesses this from the Manchester Evening News (paywalled; Manchester, UK) of 20oct1891 (emphasis mine):
One wonders what would have been the effect upon the colonel's enthusiastic nature if he had had another bottle of wine, or upon the veracious chronicler of the important speech if the colonel had accompanied his utterances by a defiant nod. It doesn't seem to have occurred to the said chronicler that the colonel was "talking through his hat," as the Americans say.
In contrast or as supplement to the possible influence of the Irish 'in his hat', press accounts in the US from 1900 propose an even earlier origin (from the 17th century):
Somebody has discovered that the slang "Talking through his hat" did not originate in America, but was first used by Moliere, the French dramatist, who in his "Miser" makes one of his characters say: "To whom I speak? I am speaking to the inside of my hat." — Philadelphia Times
Whatever the scope of the influence of the Irish 'in his hat' and the speech in Moliere's "Miser", the US origin of the phrase, and hence the British origin, is evidently from Bowery (New York) slang of the mid-to-late 19th century.
It may well be a reference to how the Mormon founder attained his early revelations. That was more common knowledge in the 19th century where this saying originates. Wikipedia describes how John Smith put a seer stone into a white stovepipe hat and then put his face into it to gain revelations from God.
Whether or not this was divine interaction, the behavior is strange and so talking through your hat means you don't know what you're talking about, or you're talking crazy, or both.