Source : Webster's Revised Unabridged Dictionary (1913)

Nest \Nest\, n. [AS. nest; akin to D. & G. nest, Sw. n["a]ste,
   L. nidus, for nisdus, Skr. n[=i]?a resting place, nest; cf.
   Lith. lizdas, Arm. neiz, Gael. & Ir. nead. Prob. from the
   particle ni down, Skr. ni + the root of E. sit, and thus
   orig., a place to sit down in. [root] 264. See {Nether}, and
   {Sit}, and cf. {Eyas}, {Nidification}, {Nye}.]
   1. The bed or receptacle prepared by a fowl for holding her
      eggs and for hatching and rearing her young.

            The birds of the air have nests.      --Matt. viii.
                                                  20.

   2. Hence: the place in which the eggs of other animals, as
      insects, turtles, etc., are laid and hatched; a snug place
      in which young animals are reared. --Bentley.

   3. A snug, comfortable, or cozy residence or situation; a
      retreat, or place of habitual resort; hence, those who
      occupy a nest, frequent a haunt, or are associated in the
      same pursuit; as, a nest of traitors; a nest of bugs.

            A little cottage, like some poor man's nest.
                                                  --Spenser.

   4. (Geol.) An aggregated mass of any ore or mineral, in an
      isolated state, within a rock.

   5. A collection of boxes, cases, or the like, of graduated
      size, each put within the one next larger.

   6. (Mech.) A compact group of pulleys, gears, springs, etc.,
      working together or collectively.

   {Nest egg}, an egg left in the nest to prevent the hen from
      forsaking it, and to induce her to lay more in the same
      place; hence, figuratively, something laid up as the
      beginning of a fund or collection. --Hudibras.

Source : WordNet®

nest egg
     n 1: a fund of money put by as a reserve [syn: {savings}]
     2: device consisting of an artificial egg left in a nest to
        induce hens to lay their eggs in it