I don't know where our peace sign came from but the Brit sign described
here comes from a distinct moment in history. At the battle of Agincourt
the French leader told his men to cut the index and middle fingers off
those damned British bowsmen after the battle--this was of course one of
the first uses of the famed British longbow. The longbow held the day
and the bowmen and their descendents give the finger(s) to their
opponents in the emphatic way described as if to say, "see, still got
them."
I believe all this is recounted in John Keegan's superb The Face of
Battle.
Randy Fertel