the veil or shroud of a temple or of an altar (see Molina; translation here by Stephanie Wood)
Alonso de Molina:
tilma tzacuilhuaztli. velo de templo, o de retablo. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 113r. col. 2. Thanks to Joe Campbell for providing the transcription.