To cross one's fingers is a hand gesture commonly used to wish for luck. Early Christians used the gesture to implore the protection of the Holy Cross. The gesture is referred to by the common expressions "cross your fingers", "keep your fingers crossed", or just "fingers crossed".
The use of the gesture is often considered by children as an excuse for telling a white lie. By extension, a similar belief is that crossing one's fingers invalidates a promise being made.
Apotropaic magic (From Ancient Greek: ἀποτρέπω, romanized: apotrépō, lit. 'to ward off') or protective magic is a type of magic intended to turn away harm or evil influences, as in deflecting misfortune or averting the evil eye. Apotropaic observances may also be practiced out of superstition or out of tradition, as in good luck charms (perhaps some token on a charm bracelet), amulets, or gestures such as crossed fingers or knocking on wood, or as part of complex rituals of social transformation such as migration. Many different objects and charms are used for protection by many peoples throughout history.