Origins
The word 'liver' names the largest internal organ of the human body, responsible for detoxification, bile production, protein synthesis, glycogen storage, and hundreds of other metabolic functions. It is one of the few English anatomical terms that is entirely native Germanic, not a Latin or Greek borrowing.
The word comes from Old English 'lifer,' from Proto-Germanic *librō. Cognates are found across the Germanic languages: German 'Leber,' Dutch 'lever,' Old Norse 'lifr,' Swedish 'lever,' and Gothic (unattested but reconstructed as *librō). The consistency of the form across Germanic branches confirms a common Proto-Germanic ancestor.
The deeper etymology beyond Proto-Germanic is disputed among historical linguists. The two main proposals are:
Proto-Indo-European Roots
First, a connection to PIE *leyp- (to smear, to stick, to be fat). Under this theory, the liver was named for its physical appearance — it is the fattiest, most glistening of the internal organs. This root also produced Greek 'lipos' (fat), which gave English 'lipid,' 'liposuction,' and 'lipolysis.' If correct, 'liver' and 'lipid' are distant cousins.
Second, a connection to the root of 'live' (PIE *leyb- or *leyp-, to live, to remain). Many ancient cultures — Babylonian, Etruscan, Greek — considered the liver the seat of life, the source of blood, and the organ most closely connected to the soul. The Babylonians and Etruscans practiced hepatoscopy, reading the livers of sacrificed animals to determine the will of the gods. If the liver's name derives from 'life,' it preserves this ancient belief in compressed form.
Neither etymology is proven, and some linguists consider both folk-etymological. But the semantic parallel across cultures is striking: Greek 'hēpar' (liver) may be related to Latin 'iecur' (liver), and both may trace to a PIE word *yēkʷr̥ (liver), which is the actual reconstructed PIE word for the organ — a word that English did not inherit through the Germanic branch.
Latin Roots
The medical and scientific term for 'liver-related' is 'hepatic,' from Greek 'hēpatikos,' from 'hēpar' (liver). This Greek root appears in 'hepatitis' (inflammation of the liver), 'hepatocyte' (liver cell), and 'hepatology' (study of liver diseases). The Latin equivalent is 'iecur,' which did not generate productive English derivatives.
The compound 'lily-livered,' meaning cowardly, dates from the sixteenth century and reflects the humoral theory of medicine. In this system, the liver was the organ that produced blood — and by extension, courage. A pale or 'lily-white' liver was thought to lack blood and therefore courage. Shakespeare used the insult memorably. The plant 'liverwort' was named in Old English for its lobed shape resembling the liver, following the medieval 'doctrine of signatures' — the belief that plants resembling body parts could treat ailments of those organs.