This really isn’t a Navy term, but it is interesting.

During World War I when trench warfare was the rule of the day the machine gun was a very important weapon. Rapid firing weapons that could stop a massed infantry charge were very important and they could tip the balance in a battle. Machine guns were also carried by a new weapon on the battle field, the airplane. Both of these weapons had one simple job to do, place as many bullets into the air as possible.

When either a pilot or infantryman said he made it the whole nine yards and lived to tell the story he was not talking about distance, he was talking about the length of a standard machine gun belt of bullets.