V for Victory has nothing to do with swearing.
V for victory has the index and middle finger upraised with the palm outward.
The index and middle finger raised with the palm inward, is associated with swearing.
During the wars with the french, English archers were far superior to the French.
When the archers were caught, the French would cut off the fingers that pulled the bow string, the index and middle fingers.
English archers would raise these finger to the French to show that they were still intact in an act of defiance, basicaly meaning up yours.
I have no doubt that QI would tell me I am wrong but thats what I have heard. :-)