The word "马上" is formed through a vivid conceptual metaphor rooted in historical context. It literally combines the characters for "horse" (马) and "above/on" (上), painting the direct image of a person being mounted on a horse. This concrete scene was culturally associated with a state of immediate readiness, whether for travel, battle, or urgent departure, which then evolved abstractly to express the idea of something happening "right now" or "immediately", as if one were already in the saddle and prepared to go.