sores from cold
瘃 refers specifically to sores or skin damage caused by cold, such as chilblains.
瘃 combines the sickness radical 疒 with the phonetic component 豖, which likely contributed the sound. The exact historical development is uncertain, but the structure suggests a condition related to illness or bodily harm.
Under the sickness roof 疒, the component 豖 looks like a pig 豕 with an extra mark, as if the pig's skin is marked by sores. Imagine a pig shivering in the cold, its skin breaking out in sores from the frost.
For ショク, picture a person with cold sores shivering and saying 'shock!' as the pain hits: shock -> ショク, and the cold shock causes the sores.