The word "上台" is formed through a direct spatial metaphor. It combines "上" (to ascend, to go up) with "台" (a platform, stage, or podium). Literally, it paints the image of a person stepping up onto a raised platform. This concrete action is then applied figuratively to represent assuming a visible position of authority (like taking office) or stepping into a public arena (like beginning a performance), where the "stage" becomes a metaphor for a position of attention or power.