jewelled necklace
瓔 centers on a decorative jewelled necklace, specifically one made with precious stones or beads.
瓔 combines 王 (jewel) with 嬰, which likely contributes the sound and possibly the idea of encircling or adorning, forming a character for a jewelled necklace.
The left side 王 (jewel) and the right side 嬰 (which visually suggests something wrapped or encircled) together picture a necklace made of jewels encircling the neck.
For エイ, imagine an elegant 'A'-list celebrity wearing a jewelled necklace: 'A' -> エイ, and the necklace sparkles with jewels.
—