The Collaborative International Dictionary of English v.0.48:

Soapwort \Soap"wort`\, n. (Bot.)
   A common plant (Saponaria officinalis) of the Pink family;
   -- so called because its bruised leaves, when agitated in
   water, produce a lather like that from soap. Called also
   Bouncing Bet.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bouncing \Boun"cing\, a.
   1. Stout; plump and healthy; lusty; buxom.
      [1913 Webster]

            Many tall and bouncing young ladies.  --Thackeray.
      [1913 Webster]

   2. Excessive; big. "A bouncing reckoning." --B. & Fl.
      [1913 Webster]

   Bouncing Bet (Bot.), the common soapwort (Saponaria
      officinalis). --Harper's Mag.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bouncing Bet
    n 1: plant of European origin having pink or white flowers and
         leaves yielding a detergent when bruised [syn: soapwort,
         hedge pink, bouncing Bet, bouncing Bess, Saponaria
         officinalis]