POP GOES THE WEASEL

https://www.phrases.org.uk/meanings/pop-goes-the-weasel.html

Pop goes the weasel Other phrases about: Animals What's the meaning of the phrase 'Pop goes the weasel'? The name of the nursery rhyme and song. What's the origin of the phrase 'Pop goes the weasel'? Like most nursery rhymes, this has some very odd imagery, which has led to much debate as to the meaning and origin of this rhyme. The origin is perhaps the easier of the two. The earliest known published version is as the title of a dance tune. A version of the tune was published in the USA in 1850 - Pop goes the Weasel for Fun and Frolic. The text accompanying the article calls it "an old English dance lately revived". References in US newspapers soon afterwards call it "the latest English dance", so it's reasonable to believe it originated in Britain. "Pop goes the weasel" is a simple tune and there are several English/Irish/Scottish country dances that are similar.
There's no doubt that Pop goes the Weaselwas a dance, popular in England in the 1850s. In 1853, The Times included a piece describing various dances that were in vogue at the time: "La Napolienne, Pop goes the Weasel, and La Tempête... the original music of the above three celebrated dances." The dance was popular enough in early 1853 for a Mr. Moutrie, in the fashionable location of Bath, to have considered it worthwhile to place an advertisement in the Bath Chronicle, offering "instruction the the highly fashionable dances" of 'Pop Goes The Weasel', 'La Tempete' and 'Coulson Quadrille'.
A newspaper advertisement by Boosey and Sons in 1854 suggests that Queen Victoria was influential in the popularity of the dance: "The new country dance 'Pop goes the weasel', introduced by her Majesty Queen Victoria." The dance didn't have lyrics as such. It was a jig and "pop goes the weasel" was shouted out at significant points to accentuate the dance.  There's no real evidence to suggest that 'Pop goes the weasel' was anything other than the nonsense name of a dance or that the meaning of 'pop' and 'weasel' merit any further investigation.  People do like to speculate though so here's the most commonly repeated 'explanation' of the meaning of the phrase, that is, that it derives from the meaning of the well-known nursery rhyme. Rhymes of this sort are repeated word of mouth and it's entirely plausible that it existed in oral form as a children's rhyme for many years before 1850. This 'Chinese whispers' repetition is also the reason for the many variations on the rhyme. Whatever version is picked as the original, it isn't easy to determine the meaning of the words. The version most commonly used in England goes like this:  Half a pound of tuppenny rice,
Half a pound of treacle.
That’s the way the money goes,
Pop goes the weasel. Up and down the City road,
In and out the Eagle,
That’s the way the money goes,
Pop goes the weasel. Every night when I go out
the monkey’s on the table.
Take a stick and knock it off
Pop goes the weasel. A penny for a ball of thread
Another for a needle,
That’s the way the money goes,
pop goes the weasel. All around the cobblers bench
the monkey chased the people;
The donkey thought ’twas all in fun,
pop goes the weasel. Some of the US versions of the rhyme are significantly different and may have an entirely different source, but using the same tune. It could be that 'money', 'monkey' and 'donkey' that appear in many of the versions are mishearings of the same word. The important words are obviously 'pop' and 'weasel'.  The phrase soon gained hold, in the US especially, although it didn't have a specific or fixed meaning; it appears to have been used just to indicate a sense of occasion - something like 'just like that'. There's an example of that in a newspaper advertisement for groceries from The Hudson North Star newspaper, April 1856 (including 2000 lbs of Extra Family Butter, whatever that is): "All Selling Cheap. To Close Out Within Sixty Days Or Pop Goes The Weasel"  Of the different meanings of the word weasel, the most commonly used today is as the name of the small carnivorous mammal. Weasels do pop their heads up when disturbed and it is quite plausible that this was the source of the name of the dance.  'Popping' is a slang term for pawning, that is, depositing articles with a pawnbroker in return for money. Weasel may be a corruption of whistle - in cockney rhyming slang 'whistle and flute' that is, suit. It could also be from another example of CRS, that is, 'weasel and stoat' -> coat.  The Eagle was a London pub, near the City Road, and a later Eagle pub still exists on the site. The lyrics of the rhyme -  Up and down the City Road,
in and out of The Eagle,
that's the way the money goes, 
pop goes the weasel  describe spending all your money on drink in the pub and subsequently pawning your suit to raise some more. The pawning and popping explanation seem to fit the meaning of the song and the rest of the lyrics (of the English version at least), so many like to believe it is the origin. For that even to be considered there would need to be a citation that pre-dates 1853 and there's no sign of that at present. Just for completeness, there's also a theory that the weasel refers to a weaver's shuttle, which makes a popping sound when the loom is in use. Again, this is mere speculation and there's no supporting evidence for it.