cubit, + hundred (by exchange for 3967), measure, post

Concise Bible Dictionary:

Many efforts have been made to ascertain the length of this measure, from which others could be calculated. Its name signifies that it was the measure of a man’s arm from the elbow to the tip of the middle finger. Of course this would vary in different persons, and some measure would have to be taken as a standard. In the Palestine Exploration this subject has not been lost sight of. Many tombs have been measured, but they give no definite result. The inscription found in the Siloam tunnel states the length of the tunnel to be 1,200 cubits, as read by Major Condor; but 1,000 cubits as interpreted by Professor Sayce. Doubtless only a round number is intended. Its length has been found to be 1,750 feet; which makes the cubit by the two interpretations, 17.5 or 21 inches. There are however many other measurements that seem to give a cubit of 16 inches. Many of the ancient stones in the base of the temple area, the breadth of the pilasters found in the north-western corner of the area, together with their distances apart, and also the Galilean synagogues, all give a measure of 16 inches. “Quarterly Statement,” Jan., 1894.
In Ezekiel 41:88I saw also the height of the house round about: the foundations of the side chambers were a full reed of six great cubits. (Ezekiel 41:8) we read of a “great cubit,” and in the commencement of the description of the future temple the reed is described as being “six cubits long by the cubit and a handbreadth” (Ezek. 40:55And behold a wall on the outside of the house round about, and in the man's hand a measuring reed of six cubits long by the cubit and an hand breadth: so he measured the breadth of the building, one reed; and the height, one reed. (Ezekiel 40:5)). This agrees with the former passage which speaks of “a full reed of six great cubits.” From this we gather that there was an ordinary cubit, and a great cubit, the difference being a handbreadth, which is accounted to be the same as the palm, a sixth of a cubit. In Deuteronomy 3:1111For only Og king of Bashan remained of the remnant of giants; behold, his bedstead was a bedstead of iron; is it not in Rabbath of the children of Ammon? nine cubits was the length thereof, and four cubits the breadth of it, after the cubit of a man. (Deuteronomy 3:11) we find a cubit “after the cubit of a man”; and in 2 Chronicles 3:33Now these are the things wherein Solomon was instructed for the building of the house of God. The length by cubits after the first measure was threescore cubits, and the breadth twenty cubits. (2 Chronicles 3:3), a cubit “after the first measure,” or “former” or “older” measure. From these passages it is clear that there were different measures called the cubit. The 16 inches above named may have been the shortest, but what was the length of the longest is quite uncertain. See WEIGHTS and MEASURES.

Strong’s Dictionary of Hebrew Words:

Transliteration:
’ammah
Phonic:
am-maw’
Meaning:
prolonged from 517; properly, a mother (i.e. unit of measure, or the fore-arm (below the elbow), i.e. a cubit; also a door-base (as a bond of the entrance)
KJV Usage:
cubit, + hundred (by exchange for 3967), measure, post

From Manners and Customs of the Bible:

The word cubit is derived directly from the Latin cubitus, the lower arm. The Hebrew word is ammah, the mother of the arm, that is, the forearm. It is evidently a measure taken from the human body; as were other measures of length among the Hebrews and other nations. There seem to be two kinds of cubits, and some say three kinds, mentioned in Scripture. In Deuteronomy 3:1111For only Og king of Bashan remained of the remnant of giants; behold, his bedstead was a bedstead of iron; is it not in Rabbath of the children of Ammon? nine cubits was the length thereof, and four cubits the breadth of it, after the cubit of a man. (Deuteronomy 3:11), we read of “the cubit of a man.” In 2 Chronicles 3:33Now these are the things wherein Solomon was instructed for the building of the house of God. The length by cubits after the first measure was threescore cubits, and the breadth twenty cubits. (2 Chronicles 3:3), “cubits after the first [or old] measure” are spoken of. In Ezekiel 41:88I saw also the height of the house round about: the foundations of the side chambers were a full reed of six great cubits. (Ezekiel 41:8), we are told of “great cubits,” each one of which, according to Ezekiel 40:55And behold a wall on the outside of the house round about, and in the man's hand a measuring reed of six cubits long by the cubit and an hand breadth: so he measured the breadth of the building, one reed; and the height, one reed. (Ezekiel 40:5), “measured a cubit and a handbreadth.” Some writers suppose these to represent three different measures of length; while others regard the first and second as identical, thus making but two kinds of cubits. Whether two or three cannot now be determined. It is no easier to decide as to the length of any one of the cubits named. Various estimates of the Mosaic cubit have been given, varying from twelve inches to twenty-two. The ancient Egyptian cubit was nearly twenty-one inches, which some of the best authorities now estimate as the length of the Mosaic. Other authorities, however, equally worthy of consideration, claim that the length of the Mosaic cubit, as applied to the Tabernacle and Temple, was eighteen inches; and that the Jews did not use the cubit of twenty-one inches—which was Babylonian as well as Egyptian—until after the captivity.