The word 机关 is formed through the metaphorical combination of two ancient concepts: 机 (jī), originally meaning the critical trigger or mechanism in a trap or device, and 关 (guān), meaning a barrier, gate, or juncture that controls passage. Together, they literally evoke the image of a complex, concealed mechanical apparatus, like the hidden workings of a trapdoor or a lock, where one part triggers the action of another. This concrete idea of an interconnected, often cunning mechanical system was later abstracted to describe any complex, pivotal, and sometimes secretive organizational system (like an "institution" or "office") or a cleverly devised plot ("scheme"), carrying the sense of something intricately designed to produce a specific, controlling outcome.