crouch, cower
竦 centers on a fearful, shrinking posture: crouching down or cowering in response to fear or awe.
竦 combines 立 (stand) with 束 (bundle), but the historical development is uncertain. It may have originally depicted a person standing stiffly or shrinking, but the exact origin is unclear.
A person 立 stands beside a tight bundle 束, but fear makes them shrink and crouch down as if trying to hide inside the bundle.
For ショウ, imagine a small child crouching in fear and letting out a soft 'show' of breath: show -> ショウ, as they cower quietly.
to freeze (from fear, etc.); to be unable to move (e.g. from surprise); to be paralyzed (with horror, etc.)
to shrug (shoulders); to duck (head); to draw back (body)
to be unable to move while seated (because of fear, surprise, etc.)
channeled apple snail (Pomacea canaliculata); golden apple snail