the source of the river; literally, the mother of the river (see Molina)
IPAspelling:
ɑːnɑːntɬi
Alonso de Molina:
anantli. madre de rio. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 6r. col. 1. Thanks to Joe Campbell for providing the transcription.