area between eye and cheek, face
臉 centers on the face, specifically the area between the eye and cheek. It can also refer to the face as a whole.
臉 combines ⺼ (flesh/body part) with 僉, which likely contributes the sound. The character originally referred to the area between the eye and cheek, later extending to the face in general.
The left side ⺼ (flesh) suggests a body part, and the right side 僉 looks like a face with features. Together they point to the area between eye and cheek, or the face.
For ケン, picture a face with a keen expression: keen -> ケン, and the face shows a sharp, keen look.
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