Snapping your fingers is a promise, so how did it come from?

Today, I suddenly questioned the origin of the custom of hooking the little finger. I looked up all kinds of statements on the internet, and finally I thought that only Wikipedia was more reliable. However, unlike the answer upstairs, I have different views on the interpretation of trilingual wiki in China, Japan and Britain. I think the source of little finger should come from American or western cultural circles.

Japanese wiki mentioned:

ゆびきり (referring to cutting, referring to cutting り) is a popular custom in modern Japan, which is ゆびきりげんまん.

We can get two pieces of information. First, ゆびきり means that the meaning of "little finger" only appears in modern Japan, which is obviously different from the meaning of ancient girls. The second one is ゆびきり. In fact, the full name at the beginning is ゆびきりげんまんんんんん.

Compared with the content in English Wikipedia.

In the United States, the little finger oath has existed since at least 1860, when the American Dictionary of Idioms listed the following accompanying promises:

Little pink, little pink bow bell,

No matter who lies

Will sink to a bad place [sic]

Never get up again.

As early as 1860, the custom of hooking the little finger has been clearly recorded. In fact, this custom may have existed in American culture earlier. Japan didn't open its doors until the Black Ship Incident in 1853, and didn't actively learn western culture until the Meiji Restoration in 1868. Unlike today's Japan, compared with the western powers at that time, Japan is only a poor small eastern country, which has no such great cultural influence and is unlikely to affect American customs. More likely, after the Meiji Restoration, Japan incorporated the American little finger swearing culture into its own culture, and created a new word びきりげんまんんんんんんんん𞖯んんんん1

And in China, we sing and hear the ballad is:

Hook, hang yourself, never change for a hundred years.

Since it is a folk song, it is a ceremony for the other party to keep its promise, it is natural to say something threatening. However, I have never read in any ancient prose that the ancients held such a ceremony when concluding an agreement (perhaps because I didn't read much). In addition, China was closed to the outside world in the19th century, and it was unlikely to spread this custom to the United States. Therefore, I tend to think that this folk song is more likely to spread from the United States or Japan to modern China. After a certain localization transformation, it has become what we hear today.