Tititl.

Headword: 
Tititl.
Principal English Translation: 

the name of a month of twenty days (the seventeenth month, according to the Florentine Codex)

James Lockhart, We People Here: Nahuatl Accounts of the Conquest of Mexico, Repertorium Columbianum v. 1 (Los Angeles: UCLA Center for Medieval and Renaissance Studies, 1993), 178.

Tititl corresponded with the start of the new year, the equivalent of January 18th, according to Chimalpahin's reckoning in the Christian calendar.

(central Mexico, seventeenth century)
Codex Chimalpahin: Society and Politics in Mexico Tenochtitlan, Tlatelolco, Culhuacan, and Other Nahuatl Altepetl in Central Mexico; The Nahuatl and Spanish Annals and Accounts Collected and Recorded by don Domingo de San Antón Muñón Chimalpahin Quauhtlehuanitzin, eds. and transl. Arthur J. O. Anderson and Susan Schroeder (Norman: University of Oklahoma Press, 1997), vol. 2, 120–121.

Attestations from sources in English: 

18 Enero. Tititl = 18 January. Tititl. (central Mexico, early seventeenth century)
Codex Chimalpahin: Society and Politics in Mexico Tenochtitlan, Tlatelolco, Culhuacan, and Other Nahuatl Altepetl in Central Mexico; The Nahuatl and Spanish Annals and Accounts Collected and Recorded by don Domingo de San Antón Muñón Chimalpahin Quauhtlehuanitzin, eds. and transl. Arthur J. O. Anderson and Susan Schroeder (Norman: University of Oklahoma Press, 1997), vol. 2, 120–121.

This feast was an observation of Ilama tecutli. The person imitating her (ixiptla) wore a white skirt (cueitl) and a white shift (huipilli). Over this she wore a star skirt (citlalli icue) with small seashells that jingled. Her sandals had white toes, woven with cotton threads. She had a shield (chimalli) covered with white clay and pasted over with eagle feathers and heron feathers, and in her other hand she held a weaving stick (tzotzopaztli).
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 2 -- The Ceremonies, no. 14, Part III, 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), 143.

ma tunpehuaca oquic CualCan [ca hueca yn Tititl = Let's get started while it is still a good time, late in Tititl. [Footnote: One of the twenty-day months of the Aztec calendar, used here as an equivalend for December. This term is from Paso y Troncoso (1902, 86); it is likely that the missing passage in the later text from Metepec had diciembre instead.](Metepec, Valley of Toluca, 1717)
In Citlalmachiyotl, The Star Sign: A Colonial Nahua Drama of the Three Kings, eds. Justyna Olko and John Sullivan, translation by Louise M. Burkhart (Warsaw: University of Warsaw, Faculty of "Artes Liberales", 2017), 18, 72.

themes: 
Textiles, Clothing
Time, Calendar, Frequency