This is rather interesting. Turns out 'soccer' is very much a British term. And the word only became a no-no when Americans started using it.
theatlantic.com: ""From this point onwards the two versions of football were distinguished by reference to their longer titles, Rugby Football and Association Football (named after the Football Association)," Szymanski writes. "The rugby football game was shortened to 'rugger,'" while "the association football game was, plausibly, shortened to 'soccer.'""
FULL STORY AND EXPLANATION HERE
(IMAGE: FLICKR CREATIVE COMMONS)