"crossing fingers"

"...still looking for a job had another interview today so crossing fingers." What does "crossing fingers" indicate?

It's not clear to me who is supposed to "cross fingers". If you are going on a job interview, and somebody says to you "I'll keep my fingers crossed for you", that means "I wish you luck and success". But I have no idea what the origin of this expression is.

Who? Here's my guess: "I'm still looking for a job. I had another interview today, so I'm crossing my fingers." You cross your fingers for luck. Perhaps the origin is the crucifix.