popotzoa.

Headword: 
popotzoa.
IPAspelling: 
popoːtsoɑː
Alonso de Molina: 

popotzoa. nino. (pret. oninopopotzo.) hinchar los carrillos, apretarse la gente, o espessarse las yeruas.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 83v. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

POPŌTZOĀ vrefl to puff out, thicken, swell / hinchar los carillos, apretarse la gente, o espesarse las yerbas (M) [(2)Zp.103,160]. In one of the two attestations Z marks the vowel of the second syllable long and in the other leaves it unmarked for length. Z glosses this as a noun 'lung.'
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 203.