unback

verb2

1. •
   (rare) To remove the back or backing from (something).

   • “When you go home,” resumed Josephine, “unback the miniature case and upon the surface opposite the painting you will find these words […]” — 1896
2. •
   (no longer used) To deprive (a horse) of its rider.

   • Her horse againe this Princesse must vnbacke, — 1599