I thank Stephen Pastis who produces the “Pearls Before Swine” cartoons for this expression, although the cartoon in which this expression was featured wasn’t one of his better creations. The expression is used to describe a person in a weak position who can’t prove their argument for lack of a witness or any solid evidence. The Phrase Finder writes “…it’s just a folksy way of describing something that has no support. The metaphor probably refers to furniture…” Stools with four, three, or even just one leg have functionality, “…but a stool without a single leg to stand on was incapable of supporting you!” 

The Phrase Finder explains that that the expression refers to an “…offering or deal that is foolishly accepted without being examined first. The expression is part of British commercial law “caveat emptor”—which is Latin for “let the buyer beware.” The expression has been around for over five hundred years and is a warning that you should check the bag (poke) to verify that you are really buying a pig and not an animal of lesser quality. As a bonus, the expression is also the origin of “letting the cat out of the bag.”

The Phrase Finder writes that the expression indicates someone is obsessed with an idea and is in a state of agitation that someone would demonstrate if they did have a bee in their bonnet. There was an earlier expression “to have bees in one’s head” that was recorded from the 16^th century. The first citation of the eventual expression located by the Phrase Finder was in “…the Reverend Phillip Doddridge Letters, 1790…”

The Word Detective writes that the phrase probably evolved from the American idiom “to talk turkey,” meaning “to speak directly and frankly, without beating around the bush.” An early form of the phrase was “to talk cold turkey,” and using “cold turkey” probably was “…a simple, uncomplicated meal, as a metaphor for simple, unadorned, direct speech.” Talking cold turkey came to mean “give it to me straight; tell me the unvarnished truth. “Cold turkey” came to mean “quit suddenly, with no tapering off…”

A recent article on theatlantic.com says “Throughout the ‘20s, records progressively became louder to take advantage of the proliferation of gramophones that had no volume knob. The phrase “put a sock in it” actually references cramming a sock into the horn of a gramophone to stifle the sound on louder recordings.”

A reader on The Word Detective asked about this phrase, writing that the gramophone origin “just sounds too, well, cute.”  The Word Detective responded that “Several word-origin books … assert [the gramophone story] as established truth, which it isn’t…. the first print citation for “put a sock in it” found so far comes from 1919.”  In that publication, the term was defined, which suggests it was recently coined.  The Phrase Finder agrees.

Word Detective goes further, using the Dictionary of Slang and Unconventional English, which “pegs ‘put a sock in it’ to early 20th century military slang use, and ties it, significantly, to another phrase popular at the time, ‘put a bung in it’ (‘bung’ being a very old English word for ‘stopper’ or ‘cork’ of the type used to seal bottles). Both phrases meant simply ‘stop talking’.”