The compound word **辛勤** is formed through the combination of two semantically related characters, **辛** (xīn), meaning "hard," "laborious," or "toilsome," and **勤** (qín), meaning "diligent," "industrious," or "frequent." Together, they create a synergistic meaning where **辛** emphasizes the aspect of hardship and exertion, while **勤** focuses on the consistent, diligent effort applied to a task. This structure is a classic example of a coordinated compound (并列式) in Chinese morphology, where two elements of similar grammatical function and related meaning merge to form a new, nuanced adjective that describes someone who works hard and tirelessly, often with a connotation of commendable dedication in the face of difficulty.