Lewis & Short

sĭlentĭārĭus, ii, m. [silentium].

  1. I. A confidential domestic servant (orig. watching for the domestic silence; cf. Sen. Ep. 47, 3), Salv. Gub. Dei, 4, 3; Inscr. Orell. 2956; 3193; cf. Becker, Gallus, 2, p. 99 (2d. ed.).
  2. II. In the later imperial period, a certain high officer at court, a privy-councillor, Cod. Just. 3, 28, 30 fin.; 15, 62, 25; Inscr. Orell. 3194.