I believe this was "coined" in WWII when describing the following: The bullets for the machine guns used in American combat planes of WW2 and since were in chains twenty-seven feet in length. Thus if a pilot was able to fire all his bullets off at one target he was said to have given his adversary 'the full nine yards'.You ever hear the phrase "the whole 9yds"? It's because A-10s have 9yards of ammo feeding each gun