The word 吻合 is formed through a vivid conceptual metaphor rooted in literal imagery. The character 吻 means "lips", and 合 means "to close" or "to join". Thus, the compound visually depicts two sets of lips coming together perfectly, creating a seamless join. This concrete image of precise alignment was then extended metaphorically to describe any two things (such as ideas, facts, or wound edges) fitting together exactly or being in complete agreement.