From A Wiki of Ice and Fire
The Cymmeri were an ancient people of the grasslands of central Essos, who established their kingdoms among the hills. They were at some point conquered and assimilated by the Tall Men. According to legend, the daughter of their greatest ruler was married by Huzhor Amai, bringing the Cymmeri under his rule. The Cymmeri wife of Amai was charged with making his armor.
The Cymmeri are the first people known to have worked iron.