to uncover oneself, or find out what was a secret (uncover a secret) (see Molina)
Alonso de Molina:
mixmana. (pret. omixman.) descubrirse, o saberse lo que era secreto. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 57r. col. 2. Thanks to Joe Campbell for providing the transcription.