The word 留下 is formed by combining two individual characters, each contributing a core concept to create a new, unified meaning. The first character, 留, visually and conceptually represents the idea of "to remain" or "to stay" (originally depicting a field with flowing liquid, suggesting something that lingers). The second character, 下, means "down" or "below", indicating a downward direction or a resulting state of being placed. When joined, the action of 留 (causing to remain) is directed or finalized by 下, resulting in the composite sense of "to leave behind", that is, to cause something or someone to remain in a place as one moves down or away from it.