Principal English Translation: 

the name of a month of twenty days
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), 176.

Orthographic Variants: 
Attestations from sources in English: 

According to the Florentine Codex, this was the sixth month, celebrated with feasts and offerings in honor of the rain god.
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), 74.

This was the sixth festival of the year, at which time a stew of maize and beans was consumed. The festival celebrated the return of rains and the hope of a good harvest. At the end of the festival sacrifices were made by drowning people in the lake. The principal priest carried a bag of incense made from paper, adorned with seashells, and filled with yauhtli in powder form.
Bernardo Ortiz de Montellano, "Las hierbas de Tláloc," Estudios de cultura náhuatl 14 (1980), 287–314, see p. 291.