fear
悚 centers on the feeling of fear, specifically a sudden, startled fear that makes one tremble or feel uneasy.
悚 combines the heart radical 忄 with 束, which likely contributes the sound and possibly the idea of being bound or constricted by fear.
The heart radical 忄 beside 束 (bundle) suggests a heart tied up in a bundle of fear, making one tremble.
For ショウ, imagine a sudden fear that makes you shout: shout -> ショウ, and your heart is bound by the shock.