Exodus 29:13

Thou shalt take all the fat that covereth the inwards. — Whole burnt offerings were, comparatively speaking, of rare occurrence in the ancient world. Usually, parts only of the victims were consumed by fire upon the altar; the greater portion was either eaten by the priests and the worshippers, or burnt elsewhere than on the altar. Among the parts regarded as most fitting to be consumed on the altar, the fat always held a high place. This is to be accounted for either by its being considered a delicacy, or by the readiness with which it caught fire and kindled into a clear bright blaze.

The caul that is above the liver — i.e., the membrane which covers the upper portion of the liver, sometimes called “the little omentum.”