亥

Glyph origin
– depiction uncertain. Some propose it depicts a plant's roots underground, possibly as the original form of. Others propose it is an animal, similar in origin to 豕.

Etymology
groups in a word-family meaning "root, germ, generative core" along with  >, , , and. He suggests the derivation 荄根 "germ, sprout, root (n.)" → 孩 "to sprout" → 亥 "sprouting stage", i.e. "the moon’s first appearance", recalling lit. "moon sprout" > "crescent moon".

See for further etymology.

Later and  graphically converged.

As for 's phonological association with the pig. Compare the following: notes is a possible match to the Austroasiatic root, but there should be a final sonorant in Old Chinese.
 * 🇨🇬, from 🇨🇬.
 * 🇨🇬 or :
 * 🇨🇬, a loan from Old Khmer.
 * 🇨🇬, a loan from Old Khmer.
 * 🇨🇬, a loan from Old Khmer.
 * 🇨🇬, a loan from Old Khmer.

Definitions

 * 1)  grass root
 * 2) twelfth of twelve earthly branches (十二支)
 * 3) pig  of the Chinese zodiac

Etymology 1
From.

Proper noun

 * 1) the, the twelfth of the twelve

Etymology 2
From.

Proper noun

 * 1) the, the twelfth of the twelve