to discuss, or think of something inside one's head (see Molina)
Alonso de Molina:
itla nitic nicnemitia. itla nitic onicnemiti. tratar, o pensar algo dentro desi, o consigo mesmo. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 43r. col. 1. Thanks to Joe Campbell for providing the transcription.