The term "出马" is formed through a metaphorical extension of its literal components: "出" meaning "to go out" or "to exit," and "马" meaning "horse." Historically, it directly described a general or commander riding out on horseback to lead troops into battle. Over time, this vivid imagery evolved into a common idiom, "亲自出马," which figuratively means for a key person—especially one with authority, skill, or expertise—to personally step in and handle a matter directly, implying that the situation is important or challenging enough to require their direct involvement, much like a commander taking the field.