I was reading a post in a forum about the Iron Maiden creatures of Ocarina of Time. To my surprise if you fixed the camera correctly you'll see Gerudo faces behind their masks. I haven't tested the validity of such a claim, but I'll add to the theory (assuming it is true).
http://www.zeldauniverse.net/forums/...kle-armor.html
I am assuming the Iron Knuckles were originally intended to be armored gerudos for bigger plans, but time restraints caused Nintendo to make Iron Maidens to be just regular enemies. However they die like regular enemies and Link doesn't kill people. So the entire Gerudo role was competely removed from the Iron Knuckle over time.