Grid iron football evolved from Rugby (the greatest game on earth!) and Rugby refers to the positions of the back players by how far back they are from the advantage line (line of scrummage- line of scrimmage). Fullback is the farthest back, half back is halfway back, Rugby doesn't use the term quarterback but you can see how the term evolved with grid iron. Grid iron distinguished itself from Rugby when the rule was changed to allow the forward pass, which Rugby doesn't allow. The forward pass is also what makes grid iron so dangerous- no amount of padding and helmets can really protect a player from a speeding linebacker over the middle!