From 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]
From WordNet (r) 3.0 (2006) :
white-livered
adj 1: easily frightened [syn: chicken, chickenhearted,
lily-livered, white-livered, yellow, yellow-
bellied]