Every great NFL defense needs a nickname. From the Purple People Eaters (Vikings) to the Steel Curtain (Steelers), the Monsters of the Midway (Bears) to the Doomsday Defense (Cowboys), the Fearsome Foursome (Rams) to the New York Sack Exchange (Jets) and the Orange Crush (Broncos) to the Legion of Boom (Seahawks), the best all got monikers.