the blackness of something that has become increasingly black (see Molina)
Orthographic Variants:
caputzauiliztli, caputzahuiliztli
Alonso de Molina:
caputzauiliztli. negregura assi. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 12v. col. 1. Thanks to Joe Campbell for providing the transcription.