Source : Webster's Revised Unabridged Dictionary (1913)

White-livered \White"-liv`ered\, a.
   Having a pale look; feeble; hence, cowardly; pusillanimous;
   dastardly.

         They must not be milksops, nor white-livered knights.
                                                  --Latimer.

Source : WordNet®

white-livered
     adj : easily frightened [syn: {chicken}, {chickenhearted}, {lily-livered},
            {yellow}, {yellow-bellied}]