Hexahydrocannabinol, also known as HHC, is not a naturally extracted hemp product; it is instead a consequence of some laboratory experimentation to dilute the strong effects of THC. You might be amazed to know that it caught the attention of scientists back in 1944, even though we have only started hearing about it just recently.
It came into existence when an American scientist added hydrogen to Delta-9 THC; the process that we call hydrogenation took place, and HHC was formed. The first experiment appreciated Cannabis-derived THC; however, companies can use hemp-derived THC for this process to ensure safety and legalization. In either case, it is simply the hydrogenated THC. It is legal when derived from hemp-based THC under the 2018 Farm Bill law.