arbitrage

French arbitrage derives from arbitrer, 'to judge or decide,' which traces back to Latin arbiter—a witness, then a judge, then a person with authority to settle disputes. In medieval French, arbitrage meant 'the act of arbitration,' a judgment rendered between disputing parties.

The financial meaning appeared in the 1700s among French currency traders who noticed price differences between exchange markets. If a bill of exchange traded at one rate in Lyon and another in Paris, a trader could buy in one city and sell in the other, pocketing the difference. This practice needed a name, and arbitrage—the art of judging between two prices—fit perfectly.

Mathieu de la Porte published the first systematic description of arbitrage in his 1722 treatise La Science des Négocians. He described how merchants compared exchange rates across European cities to find profitable discrepancies. The practice required speed, contacts in multiple cities, and capital to deploy before prices corrected.

Modern arbitrage happens in milliseconds. High-frequency trading firms spend billions on fiber-optic cables and microwave towers to shave microseconds off transaction times. In 2010, Spread Networks built a $300 million cable from Chicago to New Jersey—1,331 kilometers of fiber laid in the straightest possible line—to gain a three-millisecond advantage. The old French judge would not recognize the courtroom.