The idiom 无济于事 (wú jì yú shì) is formed through a classical Chinese grammatical structure, literally dissecting as "无" (wú, no/there is no), "济" (jì, to aid/benefit), "于" (yú, a preposition meaning 'to' or 'toward'), and "事" (shì, matter/affair). It originates from classical literary Chinese, where the pattern "[Verb] + 于 + [Object]" was common. Thus, its core meaning is "there is no aid toward the matter," conveying that something is of no help or useless in dealing with a situation. It functions as a fixed, predicative phrase where the preposition "于" links the ineffectual action ("无济") to the specific affair ("事"), resulting in the modern sense of "to no avail."