garden, farm, yard
茆 centers on a cultivated outdoor space: a garden, farm, or yard. The meanings all point to a planted area near a dwelling.
茆 combines 艹 (grass/plants) with 卯, which likely contributes a phonetic element. The exact historical development is uncertain, but the plant radical fits the garden/farm meaning.
The grass radical 艹 sits above 卯, like plants growing in a fenced plot. Picture a garden or farm yard with greenery sprouting over the enclosure.
For エン, imagine the garden as the end of a long walkway: end -> エン, and you arrive at the peaceful yard.