If you go back a couple of centuries I’ll think you will find it was called football because the game was played on foot as opposed to those games played on horseback. This article explains it a bit better:

“…The words ‘soccer’ and ‘rugger’ were in common use in England in the early 1890s at Oxford University. The words emanate from where the rules of their version of football originated. In soccer’s case, it was the formation of the Football Association. Rugger is a variation of Rugby School football rules, and later the Rugby Football Union.

The argument that soccer – being a game where the ball is only played with the foot – is the only true form of football (and it alone is therefore entitled to use the name) is fanciful.

When F.C. Morely drafted the first version of the F.A.’s football rules (1863) handling of the ball, and indeed, running with the ball in hand, were allowed whenever a player took a “fair catch” or picked the ball up on the first bounce.

Handling in soccer was eventually cut back to only the goal keeper and restarting play from the touchlines, but it was born in 1863 with recognition that handling and running with the ball were part of the game of football.

Such claims by soccer advocates also ignore the common folk origins of football, which were never restricted to just kicking the ball.

Some historians point to evidence from old English texts which refer to football being the game of the lower classes – it being called “foot-ball” simply because the game was played “on foot”, as opposed to the sport of the ruling aristocracy, which was played on horse-back.

Over recent years, both rugby codes in Australia have dropped the use of “football” from within their marketing titles. For example, the “NSW Rugby Football League” became the “NSW Rugby League”. Similarly, the NSWRFU became the NSWRU. ”

http://www.rl1908.com/History/football.htm

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