history
From Qing-dynasty poet Gong Zizhen's 《自春徂秋偶有所感触》: 一发不可牵，牵之动全身, one hair cannot be pulled; pull it and the whole body moves. Gong used the image to describe the interconnectedness of political and social problems; it has become the standard phrase for any tightly coupled system.
usage
Seven-character chengyu (most are four). Used as a standalone warning about systemic consequences: reforms, policies, organizational changes. Contrast the English 'butterfly effect,' though this idiom is older and emphasizes causal interconnection rather than chaos.
