In China, children like to make promises by hooking pinkies (勾手指) with each other and saying: "A pinkie promise must be kept for 100years." Then, they may press their thumbs together to complete the promise. Sometimes, couples will hook pinkies and promise to be together forever.
There are many theories (推测) on the beginning of the pinkie promise. Some say it comes from a nursery rhyme. Others say it was introduced from the West — born out of a love story where a man and a woman hooked fingers.
One theory is may have something to do with the role of fingers in Chinese culture. The Chinese character for "finger" also means "aim (旨)" (referring to people's thoughts). So hooking fingers can be seen as the exchanging of thoughts.
Therefore, the fingers play an important role in making an oath (盟约)： they can not only be used to complete a promise, but also be cut for making a blood oath. When someone swears (发誓) to heaven, they use their fingers to point to the sky.
Generally, hooking fingers means making a serious promise. In some gangster (黑帮) movies, a person who breaks a promise may have his little finger cut off!
Of course, this kind of thing is not very likely to happen in real life. But we can still see how important "pinkie promises" can be.
