rest, stop, cover
愒 centers on pausing or ceasing activity, with a secondary sense of covering or sheltering that likely extends from the idea of resting under cover.
愒 combines 忄 (heart/mind) with 曷, which likely contributes the sound. The exact historical development of the meaning 'rest, stop, cover' is uncertain.
The heart radical 忄 beside 曷 suggests a state of mind where one pauses or takes shelter. Imagine your heart telling you to stop and rest under a cover.
For ケイ, picture a resting person leaning against a large letter K: K -> ケイ, and the heart-shaped cushion makes the stop comfortable.