The word entered English from Old French in the early fifteenth century. Its earliest recorded use appears in an English translation of Grande Chirurgie, the authoritative surgical text of the medieval world. It was written by the French surgeon Guy de Chauliac in Avignon in 1363. The sense was medical, describing the action of driving a diseased fluid away from a swollen part of the body.
It came into English from two sources, from Old French and directly from Latin. Both routes led back to the same Latin verb, built from two elements. The first was a prefix meaning back or again. The second was a Latin verb meaning to strike through. Augustine, the fourth-century theologian, used the Latin form to describe the recoil of a thing after impact. By the time it reached English, the Latin form had been in use for over a thousand years.
Behind the Latin lay a Proto-Indo-European root, *kwet-, meaning to shake. It named the physical act of shaking something, of causing it to tremble or shudder. From that root came the Latin verb quatere, meaning to shake and to strike, used by Roman writers of the first century BC. In Latin the root branched. One branch gave percutere, the word for striking through something. Another gave quassare, the word for shattering violently. The same ancient root gave German its everyday word for shaking, schütteln.
CONCUSSION and RESCUE share the same ancient root. CONCUSSION came from Latin concutere, meaning to shake violently, from the same root as the Latin verb for shaking and striking. RESCUE came from the same ancient root by a different path, through Old French, from a Latin verb meaning to shake out or shake free.
For over a century in English the word remained in medicine. By the 1590s it had acquired a new sense, naming the echo or reverberation of a sound. By the early seventeenth century it had moved further still, naming an indirect effect or reaction from an event. Today it is the word the United Nations reaches for when describing the cascading effects of climate change, and the word journalists reach for when describing the unintended consequences of political decisions.
