The act of sealing a promise usually is followed by linking our pinkies around each other. Such a small gesture is mainly what we call a pinky promise or pinky swear. When you make a pinky promise, you can never break it! Whether it was meant to signify an oath to keep a secret or to display pledges to do or not to do something. But why pinky fingers? Why is an unbreakable promise secured with our pinkies and not our index finger, thumb, or other gestures? Where does it originate, to begin with?
According to the Japanese Folklore Dictionary written by Ajio Fukuta, the pinky promise goes way back to the Edo period (1603-1867). In Japan, the pinky promise is known as yubikiri genman (指切りげんまん), which translates to finger-cutting. Yes, it doesn't sound as sentimental as we thought it would be. This happens because the story of the pinky promise in Japan is rather dark.
It was believed to be first established in Yoshiwara, a bygone most famous red-light district in Tokyo. If you're a Demon Slayer (Kimetsu No Yaiba) enthusiast like me, you may be familiar with this name as the Entertainment District Arc took place in Yoshiwara. The birth of the pinky promise came from the story of a prostitute who had the intention to amputate her pinky finger as a sign of her commitment or eternal affection to the customer. This occurrence spread to the general public but later on, the meaning shifted. Japanese people begin to use this phrase and link their pinkies to confirm their love for each other or signify oaths.
I would love to read the Japanese encyclopedia, but I couldn't find any access to the book, and on top of that, it was written in Japanese. Since I have poor-to-almost zero knowledge in Kanji-reading, it was unfortunate that I can't provide more to the story than what was referenced on the Japanese official Collaborative Reference Database website.
Moreover, the pinky promise also existed in America as mentioned in the Bartlett's Dictionary of Americanisms published in 1848, accompanied by the following verse, "Pinky, pinky, bow-bell. Whoever tells a lie will sink down to a bad place and never rise up again." Again, that's quite a scary connotation regarding such a cute gesture in the modern-day.
In Japan, there's also a nursery rhyme about the pinky promise, and I kid you not, it's more terrifying than the American one. "Yubikiri genman, if you tell a lie, drink 1000 needles and cut a finger." This rhyme is imprinted in children's minds, especially with Japanese folklores like Momotaro, Urashima Taro, Kaguya Princess, and others that encourage children to live honestly.
The origin of the pinky promise might be spooky, although now the pinky promise is a friendly and adorable gesture, just like high fives or fist bumps. In Korea, even a modification is made to the pinky promise where they stamp each other's thumbs to seal the promises. Pinkies-linked or not, a promise is a promise; better not break it!
(HAI/MEL)