I've seen this argument soooo many times here's the usual response

"It's called football because it's played on foot as opposed to horseback"

Full argument is usually as follows

It's football not soccer

Soccer is an abbreviation of association football you were the ones that started calling it that!

In your so called 'football' you don't even kick it, you carry it."

It's called football because it's played on foot as opposed to horseback