tzoniztac.

Headword: 
tzoniztac.
Principal English Translation: 

a person with gray hair; gray-haired (see Molina and Karttunen)

IPAspelling: 
tsonistɑːk
Alonso de Molina: 

tzoniztac. persona cana.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 153v. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

TZONIZTĀC someone with gray hair / persona cana (M) [(2)Zp.25,162]. See TZON-TLI, IZTĀC.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 317.

Attestations from sources in English: 

tzoniztaque = gray-haired people (plural)

in vevetque, in jlamatque, in tzonjztaque, in quaiztaque = the old men, the old women, the white-haired ones, the white-headed ones (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, 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, 1961), 191.