the monkey

In this song "Pop goes the Weasel",
what does the monkey have to do with anything?

Here's one explanation in Cecil's column of the children's rhyme:
"Most authorities think "Pop Goes the Weasel" describes the acts of weaving, spinning, and sewing. A weasel, Tom reports, was a mechanism used by tailors, cobblers, and hatters that "popped" when the spool was full of thread."

Okay, so a weasel can be part of a machine? Well, so can a monkey. From the Merriam Webster dictionary:

mon*key [1] (noun), plural monkeys


3 : any of various machines, implements, or vessels; especially : the falling weight of a pile driver

From what I can gather, the monkey is kind of a counterweight used by the cobbler in his craft. Sometimes words can have multiple meanings and that can lead to misdirection and/or confusion. Especially when dealing with writings from the past which use older meanings of words or slang common to that period.

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The O-man.
Always do right. This will gratify some people and astonish the rest.--Mark Twain

But is there a monkey? Some versions mention a monkey, others refer to things one buys, then say, "that's the way the money goes, pop goes the weasel". The monkey could arise from people not hearing "money" correctly.