Xiuhtecuhtli.

Headword: 
Xiuhtecuhtli.
Principal English Translation: 

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.
Patrick Thomas Hajovsky, On the Lips of Others: Moteuczoma's Fame in Aztec Monuments and Rituals (Austin: University of Texas Press, 2015), 88.

Orthographic Variants: 
Xiuhteuctli, Xihuitl Tecuhtli
Attestations from sources in English: 

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)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 1 -- The Gods; No. 14, Part 2, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1950), 11.

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)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 1 -- The Gods; No. 14, Part 2, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1950), 11.