he who knows, or he who has news about something, or a person who, by his or her position, has things that pertain to him or her (see Molina)
Alonso de Molina:
machice. elsabidor, o el que tiene noticia de algo, o persona que de officio le pertenece algo. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 50v. col. 1. Thanks to Joe Campbell for providing the transcription.