The Collaborative International Dictionary of English v.0.48:

Silentiary \Si*len"ti*a*ry\ (s[-i]*l[e^]n"sh[i^]*[asl]*r[y^]),
   n. [L. silentiarius: cf. F. silenciaire. See Silence.]
   One appointed to keep silence and order in court; also, one
   sworn not to divulge secrets of state.
   [1913 Webster]