between the skin and the flesh
腠 refers to the subtle layer between the skin and the flesh, a specific anatomical boundary. Its meaning is narrow and technical, with no broader conceptual extensions.
腠 combines the flesh radical ⺼ with 奏, which likely provides the sound. The character is a specialized medical term, and its historical development beyond this phono-semantic structure is uncertain.
The flesh radical ⺼ on the left hints at body tissue, while 奏 on the right can be imagined as a layered musical performance. Picture the skin and flesh as two layers of a performance, with 腠 being the thin space between them.
For ソウ, imagine a thin layer of sound (ソウ) vibrating between the skin and flesh, like a subtle musical note from the 奏 component.