The Collaborative International Dictionary of English v.0.48:

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

   Syn: lily-livered. [1913 Webster]

              They must not be milksops, nor white-livered
              knights.                            --Latimer.
        [1913 Webster]

WordNet (r) 3.0 (2006):

white-livered
    adj 1: easily frightened [syn: chicken, chickenhearted,
           lily-livered, white-livered, yellow, yellow-
           bellied]