The word "贴心" is formed through a vivid conceptual metaphor. It combines the character for "to stick close" (贴) with the character for "heart" (心) to create a single, powerful image. This imagery suggests a quality or action that is so considerate, attentive, and understanding that it figuratively "sticks to the heart" of another person, implying an intimate closeness of care and thoughtfulness that feels as near as one's own heartbeat. The meaning is not merely the sum of its parts, but the evocative picture they paint together.