Don't Cut Off Your Pinky Finger !

The little finger, often called the pinky in American English, pinkie in Scottish English (from the Dutch word pink, "little finger"), or fifth digit in medicine, is the most ulnar and usually smallest finger of the human hand, opposite the thumb, next to the ring finger.
To pinky swear, or make a pinky promise, is the entwining of the little fingers ("pinkies") of two people to signify that a promise has been made. It is often seen in anime,
where it is called a yubikiri, means: "finger cut-off"
Pinky swearing presumably started in Japan, and may be connected to the Japanese belief that soulmates are connected by a red string of fate attached to each of their pinkies.
In Japan, the pinky swear originally indicated that the person who breaks the promise must cut off their pinky finger. In modern times, pinky swearing is a more informal way of sealing a promise. It is most common among school-age children and close friends. The pinky swear signifies a promise that cannot be broken or counteracted by the crossing of fingers or other such trickery.