tirret

plural tirrets

1. governmentA manacle, shackle, or swivel.

   […] tufted, ducally gorged, with chain reflexed over the back, & charged on the shoulder with a tirret or.

   1886, James E. Doyle, The Official Baronage of England: Showing the Succession, Dignities, and Offices of Every Peer from 1066 to 1885, with Sixteen Hundred Illustrations, page 190

   2 more examples

   Sinister, an unicorn, argent; armed, unguled, mained, tufted, ducally collared, or; on the shoulder, a tirret, or. MOTTO.

   1813, Barak Longmate (the Younger), The Pocket Peerage of England, Scotland and Ireland; ..., page 244

   A bendlet between two tirrets, over all a lion, rampant. […] On the Shield of dripstone^([sic]) of Door, a rose within a wreath; the tirrets are profusely used on the wooden ceiling and in the moulding, both external and internal. The wreath is also met with several times.

   1885, The Wiltshire Archaeological and Natural History Magazine, page 209