Were did the phrase"keep your fingers crossed" originate and how did it come to signify luck?

Answer 1

"This gesture originates from the custom of making a wish upon the cross. It was believed that the cross was a symbol of unity and that benign spirits dwelt at its intersecting point -- to wish on a cross was a figurative way of securing the wish at the intersection until it came true.

This custom dates back to pre-Christian times and, in many early European cultures, two people were required to use their index fingers to form the sign, one to make the wish and the other to support it. Over the years, the custom was modified so one person could make a wish on his/her own."

Answer 2

KEEP YOUR FINGERS CROSSED -- From "Random House Dictionary of Popular Proverbs and Sayings" by Gregory Y. Titelman: "Hope for success. The saying derives from the superstition that bad luck may be averted by making the sign of the cross. Originated in the 1920s."