to seal or put a stamp on a letter, a piece of writing, or a document (see Molina)
Alonso de Molina:
amatlacuilolmachiotia. n. (pret. onamatlacuilolmachioti.) sellar carta o escriptura. 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.