See an image that represents Xiuhteuctli in the Visual Lexicon of Aztec Hieroglyphs, ed. Stephanie Wood (Eugene, Ore.: Wired Humanities, 2020-present).
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.
Xiuhtecuhtli = 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.