the public place were notaries or scribes would write things for others (see Molina)
Alonso de Molina:
amatlacuiloloyan. el lugar publico, donde escriuen los escriuanos. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 4v. col. 2. Thanks to Joe Campbell for providing the transcription.