red rust, either whole or in pieces before being ground (see Molina)
IPAspelling:
ɑːtʃijoːtetɬ
Alonso de Molina:
achiyotetl. almagre entero, o en pedaços antes que lo muelan. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 2r. col. 1. Thanks to Joe Campbell for providing the transcription.