carbuncle
疔 refers to a carbuncle, a severe skin infection with multiple pus-filled boils. The meaning is specific to this medical condition.
疔 combines the sickness radical 疒 with 丁, which likely provides the sound. The character is used specifically for carbuncles.
The sickness enclosure 疒 surrounds 丁, like a nail (丁) piercing the skin and causing a painful carbuncle.
For テイ, imagine a doctor treating the carbuncle with a cup of tea: tea -> テイ, and the tea soothes the infection.
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