The word 胸口 is formed by combining two characters: 胸 (xiōng), meaning "chest" or "thorax", and 口 (kǒu), meaning "opening" or "mouth". It creates a visual and conceptual compound where 口 does not refer to the actual mouth but metaphorically denotes a central, hollow, or vulnerable spot, the pit, opening, or front center of the chest. Thus, the term literally pictures and pinpoints the "opening of the chest", effectively referring to the area where one might feel physical or emotional sensation.