"The word was derived from Association Football, which was the original term given to the game in the 1860s at the elite schools that spawned the sport in England. The abbreviation “Assoccer”, which became “soccer,” was used by the British upper classes of that period. When the sport was embraced by the less fortunate, the name of “soccer” was passed down. But most commoners used the word “football” to describe their new game. Nowadays, from the British Royal Family down to the passionate supporters in the terraces at Anfield (Liverpool FC), Old Trafford (Manchester United), or Stamford Bridge (Chelsea FC of London), the game is called football. "
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Just found that on a website. And also, even though I am an American, I spend a lot of time in Germany where they call it football so I have begun to refer to it as football. I find it strange that other people in America don't call it football as opposed to soccer but apparently there's a reason why.