iyac.

Headword: 
iyac.
Principal English Translation: 

something stinking (see Molina)

Orthographic Variants: 
hiiac, ihyāc
IPAspelling: 
ihyɑːk
Alonso de Molina: 

iyac. cosa hedionda.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 36v. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

IHYĀC something foul, stinking / cosa hediona (M) See (I)HYĀYĀ.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 102.

Attestations from sources in English: 

hiiac = stinking (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 10 -- The People, No. 14, Part 11, 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), 132.