The Chinese idiom **天衣无缝 (tiān yī wú fèng)** is formed through a four-character metaphorical structure originating from an ancient mythological tale. Literally translating to "heavenly clothes without seams," it directly references a story about a celestial being whose robe was woven seamlessly from a single piece of cloud or mist, possessing no stitched joins. Through this vivid imagery, the idiom was semantically extended to describe anything—such as a plan, argument, or piece of art—that is so perfectly crafted and coherent that it appears utterly natural and without any flaws or loopholes, just as a divine garment would have no visible seams. Thus, its formation moves from a concrete mythological narrative to an abstract adjective praising impeccable perfection.