Yes, to differentiate soccer and American football. But the proper French I've learnt is "le foot" as sylber said, and to me means soccer.I am pretty sure that Canadian French people call football "le soccer," however. I am certain I have seen them say this in conversation with me.
What's your source? I doubt it very much, doesn't look like Gaelic spelling to me...In Canada one says "le soccer" for "soccer" ("soccer" is actually an Irish Gaelic word, by the way), and "le football" for American football.
This is also the explanation I had heard for the origin of the word "soccer"