Have you saluted a Frenchman lately? Properly?
Before the battle of Agincourt in 1415, the French, anticipating victory over the English, proposed to cut off the middle finger of all captured English soldiers. For without the middle finger it would be impossible to draw the renowned English longbow, and therefore they would be incapable of fighting in the future. This weapon was made of the native English Yew tree and the act of drawing the longbow was known as "Plucking the Yew."
However, much to the bewilderment of the French, the English won a major upset that day and began mocking the French by waving their middle fingers at the defeated French, saying, "See, we can still Pluck the Yew!"
Over the years some "folk etymologies" have grown up around this symbolic gesture. Since "Pluck Yew" is rather difficult to say, like "pleasant mother pheasant plucker"... which is where you had to go for the feathers used on the arrows for the longbow.
The difficult consonant cluster at the beginning has gradually changed to a labiodental fricative "F" and so, sometimes the words often used in conjunction with the one-finger-salute are mistakenly thought to have something to do with an intimate encounter.
In addition, because of the pheasant feathers on the arrows, the ancient symbolic gesture is also known as "giving the bird", a natural and normal gesture towards the French by english-speaking folks since the 1400's.