a secretary; but, literally, a secret word-keeper, one who keeps secrets (see Molina)
Alonso de Molina:
ichtacatlatolpiani. secretario. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 32v. col. 2. Thanks to Joe Campbell for providing the transcription.