Why do we cross our fingers for good luck

Why do we cross our fingers for good luck?
If this a christian thing involving the cross then why is the pagan god luck involved. Luck was a pagan god right?

K French
Beavercreek, Ohio

[C K Dexter Haven]

No, Luck Skywalker was from Tatooine, not from Pagan.

[Bricker]

I'm not remotely familiar with the pagan figure Luck, but I assure you that luck (small 'l', random events operating in one's favor) is a commodity known and desired by Christians, Jews, and Muslims, as well as pagans.

I express no opinion upon the actual efficacy of crossing your fingers to create more luck in a given situation.

- Rick

[Mr Thin Skin]

Since no guesses were forthcoming, let my weight in with an actual guess.

You're making a little cross(Christian) with you fingers. Sorta like holding a cross up in front of a werewolf. Another question is why doing behind you back reverses an promise you might give.

[Ukulele Ike]

Mr. TS: Don't be holdin' no crosses up in front of werewolves. It just makes 'em testy, and they eat you slower.

Vampires, now, those guys you can hold a cross up to.

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Uke

[handy]

How com eit means something else if you do it behind your back when you say something?