large ring of fine jade
瑗 refers specifically to a large ring made of fine jade, a ceremonial or ornamental object.
瑗 combines 王 (jade) with 爰, which likely contributes the sound. The character denotes a specific type of jade ring.
The left side 王 (jade) tells you the material, and the right side 爰 looks like a hand holding something round. Picture a large, precious jade ring being held up for display.
For エン, imagine an enormous jade ring that marks the end of a long ceremony: end -> エン, and the ring is the final, precious object.