Source : Webster's Revised Unabridged Dictionary (1913)

Ducking \Duck"ing\,
   n. & a., from {Duck}, v. t. & i.

   {Ducking stool}, a stool or chair in which common scolds were
      formerly tied, and plunged into water, as a punishment.
      See {Cucking stool}. The practice of ducking began in the
      latter part of the 15th century, and prevailed until the
      early part of the 18th, and occasionally as late as the
      19th century. --Blackstone. Chambers.

Source : WordNet®

ducking stool
     n : an instrument of punishment consisting of a chair in which
         offenders were ducked in water [syn: {cucking stool}]