Football is a game that emerged in medieval England. They called it football because you played it on foot, not horseback. Medieval football is vaguely similar to the sports it shares a name with today: two teams fight to control a ball and bring it to the goal on their end of the field. In those days you could carry the ball with your hands, and the field was usually the main street in your town or village. There were tons of regional variations, and over time these variations took on their own characteristics.The town of Rugby had a set of rules people there liked, so those eventually standardized into what we call Rugby. When football came to the US it developed into Gridiron football, or American football. Back in England, the sport was standardized into more or less its modern form, and in the proccess it picked up a nickname: Soccer, from a slang convention applied to "Association football". As I understand it, this nickname wasn't very popular in England- it had a class character, and it was seen as posh, appropriative, and alienating to working class fans and players, who preferred its old name of football. Soccer is the word that caught on when the sport was introduced to the US, because we already had a sport called football. A popular urban legend is that English football fans stopped using the word soccer because it's the word American fans were using, but it's more about that class dimension I mentioned earlier.