Source : Webster's Revised Unabridged Dictionary (1913)

Quaff \Quaff\, v. t. [imp. & p. p. {Quaffed}; p. pr. & vb. n.
   {Quaffing}.] [For quach, fr. Gael. & Ir. cuach a drinking
   cup; cf. L. caucus a drinking vessel. Cf. {Quaigh}.]
   To drink with relish; to drink copiously of; to swallow in
   large draughts. ``Quaffed off the muscadel.'' --Shak.

         They eat, they drink, and in communion sweet Quaff
         immortality and joy.                     --Milton.