The name of the game
As you all know, football is an English invention. But probably not many of you know, but soccer is actually the original term for this sport. According to some legends that word soccer was invented in 1863 by an Oxford student who used the term to describe the sport he preferred.
The word football was adopted about 18 years after the first mention of soccer, only after the game became popular. In the same 1863 group of English teams came up with a standard set of rules to be used in their matches. That's how they came up with the rules for "Association Football" (football was a common name for every sport with a ball that was played on foot, so that way they distinguished this one). In the beginning soccer and rugby were games for the elite, but after their spreading to the masses soccer quickly became people's favorite, so soon Association Football became football. The first record of using that word as a name of the game is from 1881.
So, why is the word soccer still used in some countries? Well, they already had sports named football, so they chose to call the sport soccer (USA, Canada, New Zealand, Ireland and many others).