A pinky promise.
The pinky promise was brought up in Japan. Known there as the
“pinky swear”, presumably started in Japan where it is called yubikiri and often additionally confirmed with the vow "Finger cut-off, ten thousand fist-punchings, whoever lies has to swallow thousand needles”. Yubikiri genman, uso tsuitara hari senbon nomasu. The gesture may be connected to the Japanese belief that soulmates are connected by a “red string of fate”.
In 1860 the pinky swear came to America and was established into a pinky promise.
But it feels like it had less meaning then when it was called yubikiri and had little consequence when you broke the promise you had made,
also that red string of fate was no more.
In America these pinky promises are made with children and not adults, because what child would risk their pinky finger to get chopped off for breaking a promise they can’t keep?
When you intertwine your pinky with another and swear a promise, you keep that promise. If you can’t you shouldn’t have made it in the first place