The Collaborative International Dictionary of English v.0.48:

Quicksilver \Quick"sil`ver\, n. [Quick living + silver; -- so
   called from its fluidity; cf. G. quecksilber, L. argentum
   vivum. See Quick, a.] (Chem.)
   The metal mercury; -- so called from its resemblance to
   liquid silver.
   [1913 Webster]

   Quicksilver horizon, a mercurial artificial horizon. See
      under Horizon.

   Quicksilver water, a solution of mercury nitrate used in
      artificial silvering; quick water.
      [1913 Webster]