Umm… ever heard of Polo? Buzkashi? Chovgan? Pato? All of those are ball games played on horseback (except Buzkashi which is played on horseback but uses a a goat carcass instead of a ball)

Your analogy is also false because cars were invented before planes.

That was exactly my point... do you think nobody thought of kicking a ball around BEFORE they decided to break horses, train them and then push a ball around with a stick while on horseback?

To risk a valuable commodity as a horse in a game, it implies humanity was already well off enough (at least some people) to keep horses around with relative ease

My point was that the simplest form of a sport (on foot) would have likely existed (and indeed they did) WAAAAAAYYYYY before we decided to play sports on horses

At the end of the day, it seems both sources are valid: Horseback sports were the only ones officially recognized during medieval times; AS WELL AS, historical records showing games played by kicking balls from way before. Which of those 2 sources or both to a certain extent are part of the etymology of the modern word "football"