Leather radical on the left - the indexing radical. 革 pictures a stretched animal hide. Shoes were made of treated leather, so the radical anchors the meaning. Standard for leather goods: 鞭 (whip), 鞍 (saddle), 鞘 (scabbard).
Right 圭 (two stacked 土) supplies the sound - guī → xié shows audible drift, but they share an Old Chinese velar series (also seen in 街 jiē, 蛙 wā). Pure phonetic loan; the jade-tablet meaning is dormant here.
