hem, underwear
裙 centers on the lower edge of a garment and the garment worn next to the skin: a hem or underwear.
裙 combines 衤 (clothing) with 君, which likely contributes the sound. The character originally referred to a skirt or lower garment, with the modern meanings narrowing to hem and underwear.
The clothing radical 衤 beside 君 suggests a garment associated with a ruler's formal attire. Picture the hem of a royal robe or the fine underwear worn beneath it.
For クン, imagine a coon (a raccoon) peeking out from under the hem of a skirt: coon -> クン, and the hem hides the little animal.
waist-robe; pleated lower garment