The word 天真 is formed through a vivid conceptual fusion where the character 天 (heaven/nature) is combined with 真 (truth/genuine). It does not describe a literal "heavenly truth", but instead creates a poetic metaphor: it evokes the innate, original, and unspoiled state of something, much like nature in its purest form. Thus, the meaning "naive" or "innocent" emerges from this idea of being naturally true, as untouched and straightforward as heaven itself.