straw mat
莚 centers on a woven straw mat used for sitting or sleeping. It is a specific object rather than a broad abstract concept.
莚 combines 艹 (grass) with 延, which likely contributes the sound and may suggest something spread out, like a mat. The exact historical development is uncertain.
The grass top 艹 over 延 looks like woven plant material spread out flat. Picture a straw mat made of grass, stretched out on the ground.
For エン, imagine the end of a long day, and you unroll a straw mat to rest: end -> エン, and the mat is ready.
matting