In the 1415 Battle of Agincourt between the French and English as the birth of flicking the bird. The English had the best archers in Europe at the time. For the archer to use the longbow, he needed his first two fingers. Apparently, the French threatened to cut the fingers off the English longbow men. In a contemptuous gesture, the English gave the finger to the French showing they still had their fingers.
Before or after they threatened to fart in their general direction?