The word 垃圾 is formed through a common Chinese linguistic process where two characters with similar or related meanings are combined to create a single, more specific concept. Both 垃 and 圾 are ancient characters individually associated with undesirable, discarded earth or rubble, essentially dirt and debris. By pairing them, they reinforce and specify each other, solidifying into the modern concrete noun meaning "rubbish" or "garbage". This formation leverages the semantic overlap of the components to create a unified, enduring term.