I've heard several people say that Iron Knuckles are Gerudo. I've also heard the Gerudo model was used just as a basis for the entire model to make modeling the character easier. Here is my theory. The German version of the games refer to the Iron Knuckle as the "Iron Prince" , I assume the word "Prince" was used on purpose. To me, this hints that Iron Knuckles aren't just Gerudo armor worn by only females, but a somewhat common (or used to be) ancient armor used in different forms by both men and women of different races. The ones you see in OoT and Majora's Mask just happen to be the Gerudo and Ikana versions respectively. My other theory is that they could also be executioners turned soldiers, as the massive weight of their axe would allow them to perform a proper execution even if the axe is blunted, and also use their tool as a weapon in combat. I would like to hear your opinions on this.