unstiffen

verb

1. To remove the stiffness from; to relax; to make pliant.

   “We stopped here about ten o'clock this morning, and I was so tired and stiff after the long night wedged in tight in the railway carriage that I got out to get some air and unstiffen myself, instinctively clutching my fiddle-case; and a Bavarian officer on the platform, watching the train with some soldiers, saw me and came over to me at once and demanded to see my papers.”