Pinky swear

To pinky swear, or make a pinky promise, is the entwinement 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 (指切り, Japanese for "Finger Cut-off").

Example of a 3-way pinky swear

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.