The word 里面 is formed by combining two characters, each contributing a core spatial idea: 里 originally meant "village" or "community" in ancient times, evolving to mean "inside" or "interior", establishing the core concept of an inner location. The character 面 means "face", "surface", or "side", and here it specifies and particularizes that interior as a specific area or realm. Together, they create a compound where 面 acts as a suffix to 里, refining the general notion of "inside" to more concretely mean "the interior side" or "the space within".