The word "追本溯源" is formed by combining two parallel verb-object phrases: "追本" (pursue the root) and "溯源" (trace the source). Each character contributes directly: 追 means "to pursue", 本 means "root", 溯 means "to trace back", and 源 means "source". This creates a compound idiom where both phrases reinforce the same action of seeking origins, resulting in the overall meaning of investigating the fundamental cause or origin.