Lewis & Short

nīdŭlus, i, m. dim. [nidor], a little nest.

  1. I. Lit.: Ithacam illam, in asperrimis saxulis, tamquam nidulum, affixam, Cic. de Or. 1, 44, 196; Gell. 2, 29, 2.
  2. * II. Trop., a place of retirement: senectutis, Auct. ap. Plin. Ep. 6, 10, 1: opuscula mea, quia plurima evolaverunt de nidulo suo, Hier. Ep. 47, 3.