wine goblet made from horn
觶 centers on a specific type of drinking vessel: a wine goblet made from horn. It is a rare character with a narrow, concrete meaning.
觶 combines 角 (horn) with 單, which likely contributes the sound. The character originally referred to a horn-made ritual wine vessel.
The left side 角 is a horn, and the right side 單 looks like a container with a lid and base. Picture a horn carved into a goblet for wine.
For シ, imagine a single horn goblet being used in a ceremony: the word 'single' starts with シ, and the goblet is made from one horn.