A little history for you all out there......

The Battle at Agincourt (ca. 1369 AD) involved the French and the English.

The French, who were overwhelmingly favored to win the battle, threatened to cut a certain body part off of all captured English soldiers so that they could never fight again. The English won the battle. It was a major defeat for the French. When the battle was over, the English marched in front of those French soldiers who remained alive and waved the body part in question at the French in defiance.

Do you know what this body part was?

The answer:

The body part which the French proposed to cut off of the English after defeating them was, of course, the middle finger, without which would have been impossible for the English soldiers to draw the renowned English longbow. This famous weapon was made of the native English yew tree, and so the act of drawing the longbow, using the forefinger and middle finger, was known among all soldiers as "plucking yew".

When the victorious English waved their middle fingers at the defeated French, they said, "See here, we are still able to pluck the yew!" That was quickly shortened to a haughty shout of, "PLUCK YEW!" Over the years differing customs have evolved from this symbolic gesture.

Since 'pluck yew' is rather difficult to say (sort of like "pleasant mother pheasant plucker", which is who you had to go to for the feathers used on the arrows launched by the English longbow), the difficult consonant cluster at the beginning has gradually changed to a labiodental fricative "F".

Thus the words often used in conjunction with the middle-finger-salute, often mistakenly thought to have something to do with an intimate sexual encounter, were actually first used after the battle at Agincourt!

It is also interesting to note that it is because of the pheasant feathers on the arrows that the symbolic gesture is known as "giving the bird".

And yew thought yew knew everything!!! Enjoy!!!