fear, overawed
懼 centers on a deep, overwhelming fear that makes one feel small or awed. It covers both personal dread and the sense of being overawed by something greater.
懼 combines 忄 (heart) with 瞿, which likely contributes both sound and the idea of looking around fearfully, as 瞿 contains 目 (eye) and 隹 (bird), suggesting a startled bird's watchful gaze.
The heart radical 忄 beside 瞿 (a shape suggesting wide, watchful eyes) paints a picture of a heart gripped by fear, like a startled bird scanning for danger.
For ク, imagine a fearful person letting out a quiet 'coo' of awe, like a dove's soft sound: coo -> ク, and the heart trembles with overawed fear.