oompoalli.

Headword: 
oompoalli.
Principal English Translation: 

of forty in forty, or to each forty (see Molina)

Orthographic Variants: 
oompoalli
Alonso de Molina: 

oompoalli. de quarenta en quarenta, o acada vno quarenta.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 77v. col. 1. Thanks to Joe Campbell for providing the transcription.