levier

Lever comes from Old French levier, from lever (to raise), from Latin levare (to lighten, to lift). The word is about lifting — a lever is a thing that lifts. Archimedes of Syracuse described the mathematical principles of the lever around 260 BCE, though humans had been using levers for thousands of years before anyone explained why they worked. The oar, the crowbar, the seesaw — all are levers.

The lever is one of the six classical simple machines described by Renaissance engineers (the others being the wheel and axle, pulley, inclined plane, wedge, and screw). It consists of a rigid beam rotating around a fixed point called a fulcrum. By placing the fulcrum closer to the load and farther from the effort, a small force can move a heavy weight. The physics is multiplication: you trade distance for force.

The word expanded into metaphor by the seventeenth century. Political leverage, financial leverage, leveraging an advantage — the idea of a small force producing a large effect proved irresistible as a description of power dynamics. In finance, leverage means using borrowed money to amplify returns (and risks). The lever became a word for any force multiplier.

The modern lever appears in thousands of forms. Door handles are levers. Brake pedals are levers. Scissors are two levers joined at a fulcrum. The shift lever in a car, the lever on a slot machine, the lever on a circuit breaker — each is a rigid bar rotating around a fixed point. The simplest machine in the world is also the most common.