Cubit: Heb. 'ammah; i.e., "mother of the arm," the fore-arm, is a word
derived from the Latin cubitus, the lower arm. It is difficult to
determine the exact length of this measure, from the uncertainty
whether it included the entire length from the elbow to the tip of
the longest finger, or only from the elbow to the root of the hand at
the wrist. The probability is that the longer was the original cubit.
The common computation as to the length of the cubit makes it 20
inches for the ordinary cubit, and 21 inches for the sacred one.
This is the same as the Egyptian measurements. A rod or staff the
measure of a cubit is called in
(Judges 3:16) gomed, which literally
means a "cut," something "cut off." The LXX. and Vulgate render it
"span."
