What is the origin of the one-fingered salute, etymologically speaking?

Well, Keiva...one version I've heard is that in the old, old outhouse days when there was a scarcity of leaves or twigs they resorted to the finger-method. And, of course, the longest finger was the most sensible to use. And I've also heard it mentioned that some folks in a certain country (without pointing any fingers ahem, the French) still employ that method today. Don't know how reliable this all is, though.

And did you see that "flippin'-off" emoticon in the animated gallery? Unbelievable!