chet

The letter chet (also spelled het/ heth/ khet /kheth /cheth) is the eight letter of the Hebrew alphabet. There are two theories as to the etymology of the letter. One (as mentioned here and here) claims it is related to the Hebrew word chut חוט - meaning thread. The second theory (mentioned in the above sources, as well as cited by Sacks and Steinberg) is that the name of the letter derives from the word chayitz חיץ, meaning "fence, partition", and Steinberg writes that in Arabic and Syrian heth is the cognate of chayitz. This explanation seems to make more sense to me, particulary based on the shape of the letter, and can still be seen in the current Hebrew ח and the English letter H, which developed from chet.

The word chayitz derives from chutz חוץ - outside (also "except"), which also gives us the word chitzon חיצון - external.

We also find a root חצה - meaning "to divide". While I can't find a source that discusses it explicitly, I feel that חוץ and חצה are likely closely related - a fence (chayitz) divides (chotze) and leaves something outside (chutz). From the root חצה, we get such words as chetzi חצי - half and chatzot חצות - midnight. From the related root חצץ - also "to divide, to make a partition" comes the word mechitza מחיצה - partition.

As far as the etymology of חצה, Klein writes:

Phoen. and Moabite חצי (= half), Arab. hazwah (=fortune), OSArab חטי (= favor). These words show that base חצה is connected with {chetz} חץ ( = arrow). Accordingly, the original meaning of חצה probably was 'to divide by casting arrows or lots'.