an ancient measure, goblet, mean, frightened
觳 is a rare kanji with a cluster of meanings that do not share one clear center: an ancient measure, a goblet, and the abstract senses of mean or frightened. Its standalone meaning is uncertain and context-dependent.
觳 combines 角 (horn) with a right-side phonetic component that appears in several rare characters. The exact historical development is uncertain, and the modern form may be a simplification or variant.
The left side 角 suggests a horn-shaped vessel, which fits the goblet and ancient measure meanings. The right side looks complex and intimidating, like something that could frighten or seem mean.
For コク, imagine a goblet made of horn that holds exactly one コク (an invented unit name): the sound コク is the measure itself.