The Collaborative International Dictionary of English v.0.48:

Wishy-washy \Wish"y-wash`y\, a. [See Wash.]
   Thin and pale; weak; without strength or substance; --
   originally said of liquids. Fig., weak-minded; spiritless.
   [1913 Webster]

         A weak wishy-washy man who had hardly any mind of his
         own.                                     --A. Trollope.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wishy-washy \Wish"y-wash`y\, n.
   A weak or thin drink or liquor; wish-wash.
   [1913 Webster]

WordNet (r) 3.0 (2006):

wishy-washy
    adj 1: weak in willpower, courage or vitality [syn: namby-
           pamby, gutless, spineless, wishy-washy]