The word 肋骨 is formed by combining two pictographic and conceptual characters. The first character, 肋, originally depicted the side of the human torso (with the 月 "flesh" radical and the component 力 suggesting strength or structure), specifically referring to the flank or rib area. It is then combined with 骨, which is a pictograph of a skeleton or bones. Together, they create a direct, descriptive compound meaning "the bones of the flank", which precisely and visually defines the anatomical ribs.