The Collaborative International Dictionary of English v.0.48:
Millrind \Mill"rind`\ (m[i^]l"r[imac]nd`), Millrynd \Mill"rynd`\ (m[i^]l"r[imac]nd`), n. [Mill + rynd.] (Her.) A figure supposed to represent the iron which holds a millstone by being set into its center. [1913 Webster]