Lilly Livered

Can anyone please tell me where the term ' lilly livered' came from ?

Thanks in advance.
Pauline

Lilies are usually white, liver is full of blood and should be dark red/brown. to be "lily-livered" is to be lacking in full-bloodedness, sangfroid or other attribute based upon being bloody, bold and absolute. doubtless The Bard made reference to it.