Now, I'm sure if you just Google it, there's some pretty simple historical or cultural reasons why the modern day, mostly hand-based sport of American football is called what it is, like it was based on an earlier sport like rugby football that did involve more footwork, but I've recently been reading the teachings of Ayn Rand, and I feel that searching for other people's answers on Google would just be parasitically sponging off their work. As a strong, self-reliant individual, I should make up the answers myself, without leaning on the crutch of "research." Because when I go live in a compound in the desert with the other geniuses, I'm not going to have access to Google. I'll have to answer all historical and science questions by relying on my own imagination.
This is how my imagination pictures George Washington, for example.
So, all that said, my intuition is telling me that when football was first invented in America, in the 1300s or thereabouts, it was originally played with an actual human foot. America was a savage place back then, and executions were such a common way of dealing with crimes that there were too many body parts to deal with. Arms and legs could be used for furniture, hands made good coat hooks, and heads were round enough to be used for basketball, but nobody could think of a use for feet, and they kept piling up.