Liver, from the Anglo-Saxon word for liver, lifer. It seems logical that the etymology of the word is somehow related to "life" but no one knows for certain. It is interesting to note that the German word for liver is die Leber, and the German verb leben is "to live".
Hepar, Greek for liver, is the source of the combining form seen in words such as hepatic, hepatitis, and heparin (which was first isolated from the liver cells of dogs).
The Latin word for liver, jecur, doesn't show up anywhere in anatomy or medicine, or in any of the Romance languages. Strangely, the Spanish, French, and Italian words for liver (higato, foie, and fegato respectively) all stem from the Latin word ficatum, "stuffed with figs", whose link with the liver is through an ancient Roman dinner specialty: jecur ficatum: liver and figs.
It was long believed that the liver was source of the body's blood and lymph; when this was shown not to be true, the organ lost favor amongst anatomists and physiologists. Its stature was revived in the 19th century by the father of homeostatic theory, the French physiologist Claude Bernard, who recognized many of the organs vital functions; indeed we now know of at least 50 ways, as Paul Simon almost sang, to love your liver.