The Chinese idiom "强弩之末" is formed by sequentially combining the characters for "strong" (强), "crossbow" (弩), the possessive particle "之" meaning "of", and "end" (末), resulting in the literal phrase "the end of a strong crossbow". This construction directly references the historical observation that a crossbow's arrow loses its force at the end of its flight, with the characters collectively depicting this scenario to convey a metaphorical meaning of once-powerful strength now in decline.