high, steep, towering, stern
埈 centers on a steep, towering height, often with a stern or imposing quality. The meanings 'high', 'steep', 'towering', and 'stern' all describe something that rises sharply and commands respect.
埈 combines 土 (earth) with 夋, which likely contributes the sound and the idea of something high or steep. The exact historical development is uncertain, but the component 夋 appears in several characters related to height or sharpness.
The left side is 土 (earth), and the right side 夋 looks like a steep, towering shape. Picture a tall earthen cliff rising sharply from the ground, stern and imposing.
For シュン, imagine a towering cliff that is so steep it makes you say 'shun' (as in shun away) because it's too dangerous to approach. The stern height shuns you away: shun -> シュン.