I’ll try to remember to cite some stuff on this. May take a day or so.
Basically, it goes back to the original rules of football a century ago. It is only recently (maybe 60 years) that the forward pass was even introduced. Before that, going back to the '20s and '30s teams of the Packers (and by default all lesser teams ), it was pretty much rushing and kicking. The forward pass was a revolution to American football. And not welcomed when introduced at the time.
Before 1940 there was no definitive positions of quarterback, halfback, fullback, nor tight end. You had a center setting the ball, a guy taking the snap, and someone running the ball. There were some men that lined up eligible to be a “ball in play” guy, as it were. But if the QB threw the ball, it had to be behind the line of scrimmage. Hence, the forward pass being such a huge revolution in football.
That’s a very wordy answer to the reply, but hopefully a glimpse into why we call it football. It was originally based on kicking the ball, as running it was rather tough when you couldn’t throw the ball for 30+ yards in a play.