one who discovers or manifests another's blame or guilt; or, one who denounces (see Molina)
Alonso de Molina:
tetlatlacolnextiani. descubridor o manifestador de culpa agena, o denunciador. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 109v. col. 1. Thanks to Joe Campbell for providing the transcription.