But actually comes from American Football where the last nine yards before the End Zone are recognised as the most difficult to traverse with your four downs. So the whole nine yards is to provide maximum effort against maximum adversity or to put it another way give it everything you’ve got.

Anne (being a bit pedantic)

That’s where I heard the term originated and I think that American football predates belted ammunition by a good few years. American football actaully came about because the Americans couldn’t master rugby 😀