The word 阴茎 is formed through direct anatomical metaphor. The character 阴 (yīn) here denotes the private or concealed area of the body, while 茎 (jīng) literally means "stem" or "stalk". Thus, the term conceptually constructs the meaning by combining the idea of a "private part" with the visual and structural similarity of a plant's stem, resulting in a descriptive, euphemistic compound for the male organ.