why the name football?

I understand from my old history professor that since American football was derived from both rugby and soccer, it was called football here. He even mentioned at one time, that football was actually called Gridiron football because of the yard lines. BTW, this old professor of mine was a good old boy Navy WW2 vet with an unique style of wearing Hawaiian shirts every day, and walking with a cane. Also, when I visited New Zealand in 1992, they referred our game as Gridiron. The women actually swoon over ya when you mention you're a Gridiron player!