Phrase equivalent to "Everything that is available." Has nothing to do with football. In fact, the phrase comes from the fact that fighter planes are equipped with belt-fed machine guns. When the belts are laid out before loading, they measure nine yards in length. If a pilot were to empty his plane's guns into a target, he'd be giving it the "whole nine yards."

The length of a belt of machine-gun ammuition used in some WWII fighter plains

Does not come from military or football. It relates to the clothing industry. It is a term that tailors have used since the 1900's for denoting the extent that one wishes to invest in a custom-made suit. It takes exactly nine square yards of material to create a man's three-piece suit. If an individual desires a suit that is tailored to the "hilt" (double lined, etc.), he would request that the tailor should proceed with "the whole nine yards." Anything shy of nine yards would mean various alterations. This would lessen the overall quality of the suit.

Used since the 18th century to describe a ship.
'Ship' is a pretty homogenous term these days, but back then, to describe a vessel as a 'true' ship, it had to have 3 masts (fore, main, and mizzen) and on each of these were 3 sails (main, top, and topgallant) suspended from horizontal 'yards'. To handle so many sails, a fairly large crew is required. Warships carried much, much larger crews than merchantmen, and so it was only warships and the large, prestigeous merchant ships such as East Indiamen that could be described as having 'the whole (or full) nine yards'.