The Chinese word 卖力 (màilì), meaning "to work hard" or "to exert oneself", is a compound formed through a metaphorical combination: the character 卖 (mài) means "to sell", and 力 (lì) means "strength" or "effort". Together, they create the vivid figurative sense of "selling one's strength", implying the full dedication and expenditure of one's energy and effort towards a task, as if offering one's labor completely to the endeavor.