Holding our Fingers

My boss at work just called me to let me know that they are מחזיקים את האצבעות ("holding their fingers") for me, that I may do well in my exam tomorrow. While thanking him for the thought, I couldn't help thinking about this phrase, which I had heard previously, but never got around to writing about (and thought, unblogged, is such a fleeting thing, don't you find?).

The question is, I think, obvious - what is the relationship of the above to the phrase "crossing our fingers"? The wise web-page "Words to the Wise: Your Etymological Queries Answered" offers the far-less-certain-than-I-would-have-expected hypothesis that the latter is connected to the crucifixion of Jesus, with possible pagan precursors (cf. on both counts "touch wood" - see, for instance, this potentially unreliable resource which backs me up), which would then suggest that the Hebrew phrase is a modern spin-off with the deletion of the Christianity reference (cf. the "plus" sign used in some Israeli text-books, which is missing the "south" pointing axis, leaving it the shape of an inverted squat upper case "T").

And from here, I throw the floor open to anyone who can shed further light on the origin of the Hebrew phrase. I hope there are some interesting answers - otherwise, what a waste of a post (after all, blogspace is not cheap) ...