Well that explains it…

Heraldic Colours (or Tinctures) | Patrick Baty – Historical paint consultant: “The story appeared in Charles Perrault’s Histoires ou contes du temps passé avec des moralités, which was published in 1697. It has been suggested that pantoufle de vair (fur slipper) might have been mistaken for pantoufle de verre (glass slipper).”

Words matter.