Xolotl.

Elizabeth Hill Boone notes that "Seler regards Xolotl as the canine god who conducts the sun each evening to the underworld." She adds that Xolotl might be the sun as well as Venus, the evening star, and "an Aztec greenstone sculpture of Xolotl depicts him as wearing a sun disk on his back." She suspects that he is Venus "as the Evening Star but also Venus in the underworld."
Elizabeth Hill Boone, Painted Architecture (1985), 132.

James Maffie reminds us that Xolotl ensures the movement of the sun, and he is also the deity associated with "monsters, deforming diseases, and deformities."
James Maffie, Aztec Philosophy (2014), 206).

anoço tozquaxolotl = or the yellow Xolotl head (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 8 -- Kings and Lords, no. 14, Part IX, 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, 1951), 74.

tozquaxolotl iquetzaltemal, coztic teucujtlaio, toçehoatl inamjc, coztic teucujtlatl injc motlotloujtec, xoxouhquj quaxolotl, quetzallo coztic teucujtlaio in jnamic xoxouhquj eoatl.
Iztac quaxolotl, quetzallo, coztic teucujtlaio in jnamjc iztac eoatl. Chichiltic quaxolotl, quetzallo, coztic teucujtlaio, in jeoaio, çan no chichiltic. = The Xolotl head of yellow parrot feathers, with balls of quetzal feathers, was ornamented with gold. With it belonged a shirt of yellow parrot feathers with hawk scratch decorations in gold.
The blue Xolotl head was ornamented with quetzal feathers and gold. With it belonged a blue shirt. The white Xolotl head was ornamented with quetzal feathers and gold. With it belonged a white shirt. The bright red Xolotl head was ornamented with quetzal feathers and gold; its shirt was likewise bright red. (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 8 -- Kings and Lords, no. 14, Part IX, 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, 1951), 34.

Ypan onpoali yhuá chi come xihuitl oazico yn Pilli. Xolotl, ohuallaque hoc yeintin tlatoque = In the forty and seventh year after the noble Xolotl arrived, another three rulers came
Anónimo mexicano, ed. Richley H. Crapo and Bonnie Glass-Coffin (Logan, UT: Utah State University Press, 2005), 16.

Xolotl, the Chichimec ruler is said to have died at the age of 200, after ruling 112 years; his son Nopaltzin inherited his rule; also, a name given to campesinos in the sixteenth century in what is now the state of Morelos
Anónimo mexicano, ed. Richley H. Crapo and Bonnie Glass-Coffin (Logan, UT: Utah State University Press, 2005), 18.
ymach y vevetl ytoca xolotl = Here is Huehuetl's nephew named Xolotl. (Cuernavaca region, ca. 1540s)
The Book of Tributes: Early Sixteenth-Century Nahuatl Censuses from Morelos, ed. and transl. S. L. Cline, (Los Angeles: UCLA Latin American Center Publications, 1993), 162–163.

The Códice Xolotl is a historical manuscript held in the French national library in Paris. For an excellent study of this manuscript, see the work of Marc Thouvenot.
Marc Thouvenot, http://thouvenotmarc.com/textos/codice_xolotl.html.