I remembered this posted to /r/Christianity yesterday https://iconreader.wordpress.com/2011/05/26/what-does-this-hand-gesture-mean-in-icons/ :)

It spells out Jesus Christ on your hand in Greek. The index finger makes I, the middle finger makes C, the thumb and ring finger cross to make X, and the little finger curls to make C. IC XC is an abbreviation for Jesus Christ.