FOOT BACK is a term used in football to describe the position of a defender. The term is used to describe a player who stands behind the line of scrimmage and is responsible for defending against the opposing team's running plays. The term HEEL, which is a four-letter word, is used to refer to the back of the foot, which is the area of the foot that is closest to the ground. This position is important for defenders as it allows them to react quickly to the opposing team's running plays.