What does "Pop Goes the Weasel" mean? And what is its origin?

It was a very old English dance tune originally. A weasel is a spinner's weasel, a mechanical yarn-winder that repetitively and tediously "pops". The lyrics are different in America from those in England. In the English version, it's all about poverty in the 19th century: the first two lines of each verse show how little money people earn and how quickly the far-too-little money goes (on not much food, or drinking in the pub), and then "That's the way the money goes" and then each verse ends on that tedious repetitive Pop! goes the weasel, sort of rubbing it in about how hard you work for how little money

PS This is how it goes in England nothing to do with mulberry bushes - that's a different one!) -

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.

For you may try to sew and sew,

But you'll never make anything regal,

That’s the way the money goes,

Pop! goes the weasel.

I believe it's just a silly fun song--Round and round the mulberry bush, the monkey chased the weasel, that's the way the money goes--pop goes the weasel.