silver dross, silver dregs, what is left over from mining silver (see Molina)
Orthographic Variants:
iztac teocuitlatl ycuitl
Alonso de Molina:
iztac teocuitlatl ycuitl. escoria de plata. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 49r. col. 2. Thanks to Joe Campbell for providing the transcription.