spasms or convulsions in young children, caused by indigestion
瘲 centers on involuntary muscle contractions in young children, specifically spasms or convulsions linked to digestive upset.
瘲 combines 疒 (sickness) with 從, which likely contributes the sound and may relate to following or accompanying, but the exact historical development is uncertain.
The sickness enclosure 疒 wraps around 從, which looks like a person following. Picture a child's body following involuntary muscle jerks caused by indigestion.
For ショウ, imagine a child's stomach showing signs of indigestion, leading to spasms: show -> ショウ.