This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
懁 combines the heart radical 忄 with the phonetic component 睘. The exact historical development is uncertain, but it likely originally expressed a strong emotion or intensity, consistent with the reading はげ.しい (fierce, violent).
The heart radical 忄 suggests an emotion, and the right side 睘 looks complex and intense. Imagine a fierce, swirling emotion that is hard to contain.
For ケン, picture a fierce person named Ken whose intense emotions match the heart radical: Ken -> ケン.