He was sometimes referred to by the name King Curl-Nose or Curl-Snout before the hieroglyphs for his name were deciphered phonetically.
Nun Yax Ayin was a son of Spearthrower Owl, a lord of Teotihuacan (probably that city's king) in Central Mexico. The instalation of a Teotihuacano noble on the throne of Tikal marks a high point of Teotihuacan influence in the central Maya lowlands.
Nun Yax Ayin may have been a child or youth at the time of his corrination, and the early years of his reign seems to have been dominated by one of his father's generals, Siyah K'ak', in a sort of regency.
He was succeeded as ruler of Tikal by his son Siyah Chan K'awil, probably in 411.