寸
スン, す, みき
measurement, foot/10
JLPT1 G6 S3 F1669
The relevant bronzeware inscription form is 又 hand + a line, indicating a hand or (thin) finger settled upon another object (such as in taking a person's pulse) → *unit of measurement* (approximately that of a finger). In characters such as 耐 將 寺 尋 and 導, 寸 functions as an action indicator.
[Full Kanji Etymology List]