why not the longbow event?
Hundred Years War:
25 October 1415, the Battle of Agincourt/Azincourt.
As you know, at that time the British appeared on the battlefield armed whit the inedited longbow , the arc length. Contraption which the French had not yet experienced the destructive power: considering it a simple bow and sure they defeats the enemy, they showed the middle finger to english (from here 'the finger'), while whit other hand made a sign to cut it. In essence, they mocked the English, promising them, once taken prisoner after the inevitable victory, cutting off his finger so as to prevent, in future, to pull the bow . Some French, more swaggering than others, went further, expressing by gestures to the Henry V 's archers intention to cut them even arm. And from here the "umbrella act" (Bras d'honneur) .The great weapon of the English army were archers.They used the index finger and middle finger every time they shoot an arrow.It was for this that every archer captured by the French were amputated fingers.From this episode comes the gesture of the middle finger and index finger raised with the back of hand.This was in fact the act ,that the English archers not captured by the French,showed to enemies before every battle,the classic "V" still used
in a gesture of victory.
(Needless remind to readers that for the French of Charles VI was the debacle: left on the field over 10 thousand men against the 500 British dead. But we must add that "la Pucelle d'Orléans" in October 1415 was three years old. At thirteen she began to hear 'voices' and seventeen stormed Orleans washing so the shame of Agincourt/Azincourt).