toward the middle, interior, inside of something (see Molina)
Alonso de Molina:
tlaticpa. hazia dentro, o delo interior. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 136v. col. 1. Thanks to Joe Campbell for providing the transcription.