pendant girdle ornament
璲 refers to a specific type of jade ornament worn as a pendant on a girdle or sash.
璲 combines 王 (jade) with 遂, which likely contributes the sound. The character was created to name a specific jade girdle ornament.
The left side is 王 (jade), and the right side is 遂 (accomplish). Picture a jade pendant that accomplishes the task of decorating a girdle.
For スイ, imagine a swaying jade pendant: sway -> スイ, and the ornament sways as you walk.