to reduce something by half or to the middle (see Molina)
Alonso de Molina:
nepantla nicquixtia. (pret. nepantla oniquixti.) reduzir algo al medio. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 69r. col. 1. Thanks to Joe Campbell for providing the transcription.