Personally I like this explanation....
lol
Lets take a little history lesson. "Football" as we know it today, started centuries ago in a country far, far, away. However, it wasn't called "Football" and it wasn't even "Football" as we know it today. Football was discovered by college students who wanted to play a different sport. They would've played the other sports, but they were just too boring. Years ago, these college students took a look at the available sports. Rugby and Soccer were the two main sports that influenced their "Football" ideas. So technically, "Football" is a form of Soccer.
Anyway, I'll skip the rest of the history, since it's not important. What IS important is how "Football" was played back in the day. The college students decided that they wanted a "rougher" sport that was similar to soccer and rugby. So, they made "Football". There were no rules, except to get the ball to the goal. So, as a result, there tended to be a lot of kicking. Since you use your foot to kick people, and since there is a ball in the game, they decided to call it football.