to start, tremble with fear
觫 centers on a sudden, involuntary physical reaction to fear: starting or trembling with fright. The two given meanings are closely linked as aspects of the same fear response.
觫 combines 角 (horn) with 束 (bundle). The exact historical development is uncertain, but it likely relates to the idea of a horned animal starting or trembling, with 束 possibly contributing a phonetic element.
Imagine a horned animal (角) suddenly startled by a tight bundle (束) falling nearby. The animal starts and trembles with fear, capturing both meanings of 觫.
For ソク, picture a sock puppet shaped like a horned animal trembling in fear: sock -> ソク, and the puppet's sudden movement makes you start.
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