This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
忺 combines the heart radical 忄 with 欠, but the exact historical development is uncertain. It may have originally expressed a feeling or desire, but no clear meaning survives in modern usage.
With a heart 忄 beside a gaping mouth 欠, imagine a person yearning for something, but the exact meaning is unclear.
For ケン, imagine Ken, a person with a longing heart, standing beside a gaping mouth: Ken -> ケン.