nahuipilli.

Headword: 
nahuipilli.
Principal English Translation: 

eighty pieces, tortilla, mats, or cloths (used for counting things that are flat and thin)

Orthographic Variants: 
nauipilli
Alonso de Molina: 

nauipilli. ochenta pliegos, tortillas esteras, o mantas.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 064r. col. 1. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

The construction is 4 x 20 = 80.

themes: 
Numbers, Math