The word 跪下 is formed through the direct combination of two characters: 跪, which depicts the act of bending the knees (composed of a "foot" radical 足 and 危, suggesting a precarious or bent posture), and 下, meaning "downward" or "below". Together, they sequentially depict the physical action of first bending the knees into a kneeling posture (跪) and then moving the upper body downward (下) into a full kowtow or prostrate position, forming a single compound that visually and conceptually represents the complete motion of prostration.