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]