Japanese children seal a promise by hooking their little fingers and chanting: Yubikiri genman, uso tsuitara hari senbon nomasu. “Cut the finger, ten thousand blows. If you lie, you swallow a thousand needles.”
Genman means striking someone ten thousand times with a fist. Yubikiri, cutting the finger, is said to go back to Edo-period courtesans, who cut off a fingertip and gave it to a man as proof of lasting love.