colic, stomach ache
疝 centers on sharp, cramping abdominal pain: colic or a severe stomach ache.
疝 combines 疒 (sickness) with 山, which likely provides the sound. The character is used specifically for colic or abdominal pain.
The sickness enclosure 疒 wraps around a mountain 山. Picture a sharp, rocky mountain inside your stomach causing colic pain.
For セン, imagine a sen (cent) coin stuck in your stomach, causing a colic ache: sen -> セン, and the pain is like a mountain inside you.
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