it certainly should be so (really a phrase, composed of ahmo za[n]) Translation provided by Joe Campbell, personal communication, March 2011.
Orthographic Variants:
amoça, amo za, ahmo za, ahmo zan, amo zan, amo ça
Alonso de Molina:
amoza. aosadas que deue ello de ser assi. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 5r. col. 1. Thanks to Joe Campbell for providing the transcription.