There have been attachments one makes to augment the fists since antiquity. India has the Kattar. The Greeks wrapped their hands in cloth and spikes before Pancration contests. Street brawlers in England would wrap broken glass around their fists. Brass knuckles are misnamed. Most are actually steel. But F=ma. So increase the mass and you increase the force of the fist. Not to mention you are essentially adding a cutting edge to your knuckles. They are legal in most states but are considered concealed weapons in others. Armies from the Wehrmacht to the Argentinians to the Royal Marines have had knuckle augment devices issued to soldiers. Like everything else, people figure out how to make them beautiful.