From WordNet (r) 2.0 (August 2003) [wn]:
lily-livered
adj : easily frightened [syn: chicken, chickenhearted,
white-livered, yellow, yellow-bellied]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Lily-livered \Lil"y-liv`ered\ (l[i^]l"[y^]-l[i^]v`[~e]rd), a.
White-livered; cowardly.
[1913 Webster]