this deity was one of the earliest known gods of Mesoamerica, the "old, old" god of fire; references to Xiuhtecuhtli are prominent in the Templo Mayor, even if he appears as a "minor god" in the Florentine Codex, according to Leonardo López Luján (referenced by Patrick Hajovsky); Hajovsky adds that "Xiuhtecuhtli conflates notions of turquoise as fire-heat (tonalli) and time, and as H. B. Nicholson attests, he was 'the archetype of all rulers." These attributes originated in the father of Tezcatlipoca, who was Huehueteotl-Xiuhtecuhtli, also attributed as the "progenitor of all the gods" according to Thelma Sullivan.
The term xihuitl, besides being turquoise, herbs, and year, can have fire and flame associations. These may come from this divine figure/lord.
Xiuhtecutli: ixcoçauhquj, yoan cueçaltzin. Jehoatl motocaiotia in tletl, anoço veue teutl yoan tota: = Turquoise Lord (Xiuhtecutli)—the yellow faced one, the holy flame. This one was known as fire, {as} the old god, {as} our father. (central Mexico, sixteenth century)
The Turquoise Lord, a little or lesser god, considered to be a very old god, a fire deity; he "scorched the fields" and warmed people, burned people, and was associated with cooking and the burning of food (central Mexico, sixteenth century)