What is "cramp ring"

Cramp \Cramp\ (kr[a^]mp), n. [OE. crampe, craumpe; akin to D. & Sw. kramp, Dan. krampe, G. krampf (whence F. crampe), Icel. krappr strait, narrow, and to E. crimp, crumple; cf. cram. See Grape.]

1. That which confines or contracts; a restraint; a shackle; a hindrance.

   A narrow fortune is a cramp to a great mind.
   --L'Estrange.

   Crippling his pleasures with the cramp of fear.
   --Cowper.

2. (Masonry) A device, usually of iron bent at the ends, used to hold together blocks of stone, timbers, etc.; a cramp iron.

3. (Carp.) A rectangular frame, with a tightening screw, used for compressing the joints of framework, etc.

4. A piece of wood having a curve corresponding to that of the upper part of the instep, on which the upper leather of a boot is stretched to give it the requisite shape.

5. (Med.) A spasmodic and painful involuntary contraction of a muscle or muscles, as of the leg.

   The cramp, divers nights, gripeth him in his legs.
   --Sir T. More.

6. (Med.) A paralysis of certain muscles due to excessive use; as, writer's cramp; milker's cramp, etc.

   Cramp bone, the patella of a sheep; -- formerly used as a charm for the cramp.
   --Halliwell. ``He could turn cramp bones into chess men.''
   --Dickens.

   Cramp ring, a ring formerly supposed to have virtue in averting or curing cramp, as having been consecrated by one of the kings of England on Good Friday.

n. (context now historical English) A ring worn to prevent cramp, epilepsy and associated diseases, especially one specifically blessed by an English monarch before the Reformation.