>>724911496
Stolen from another thread because it was very educational:
In the early days of the sport there were two competing rulesets, the more traditional one that allowed the ball to be picked up and carried, and a newer one that didn't. The ruleset that disallowed the carry was popular with a group of colleges and universities in England who all agreed to unify their rules and league, so took to calling it Association Football, whereas the other ruleset was dominated by the Rugby school so their version was called Rugby Football.
To help differentiate them in common discussion, people began calling Rugby Football 'rugby', and Association Football was called 'association' which was often shortened to 'socca' in slang. This got an official spelling later on as soccer. Outside of the anglosphere where rugby never gained a foothold, they instead always called soccer 'football'. The Brits didn't start deprecating 'soccer' until after WW2, mainly to spite the Americans.
You see vestiges of the older anglo affinity for the term in other anglophone countries like Australia and South Africa where they typically use soccer.
The reason American football is called that is because the reverse was true; soccer never gained any real popularity but rugby did. Because it was called Rugby Football back then, it got simplified to just 'football' because there was no competing ruleset also using that name.
