Some "good luck" sayings include "break a leg," which people originally said to actors in superstitious theater settings, and "fingers crossed," which originated as a way to make a wish by forming a cross with the fingers. Another popular "good luck" saying is "Godspeed."
The "good luck" saying "break a leg" is a saying that people traditionally used to wish theater actors a good performance. It started when Yiddish theater members began using the German phrase "hals und bienbruch," which means "break your neck and leg." There are many old theater superstitions involving karma, such as the belief that if a person says something, the opposite occurs. Therefore, by saying "break a leg" to an actor, a person causes the opposite to occur and bestows good luck upon the actor.
The saying "fingers crossed" comes from the Christian religion. In the past, many Christians believed that an individual who crossed her index finger over another person's finger granted that person a wish. Over time this belief became associated with crossing the fingers using two separate hands and was eventually simplified to crossing two fingers using one hand.
The saying "Godspeed" is from the Middle English phrase "God spede," which means "May God prosper you." It originated in the 15th century, and people use it to wish someone starting a journey or a new venture good fortune.