the West; literally, the sun's entering place (where the sun goes down) (see Molina)
Orthographic Variants:
tonatiuh iaquian
Alonso de Molina:
tonatiuh iaquian. el poniente. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 149v. col. 1. Thanks to Joe Campbell for providing the transcription.