capax

Capacitor comes from Latin capax, meaning 'able to hold' or 'capable,' from the verb capere, to take or hold. But the earliest electrical devices weren't called capacitors at all. When Ewald Georg von Kleist and Pieter van Musschenbroek independently created what became known as the Leyden jar around 1745, scientists called it a 'condenser'—a device to condense electrical charge. The word capax was there in the Latin, but nobody was using it yet.

Michael Faraday, the English physicist and chemist, used capax repeatedly in his electrical writings in the 1820s. When the scientific community settled on standardized terminology, they chose 'capacitor' to describe any device that stores electrical charge—drawing directly from the Latin word that named the fundamental property: capacity to hold. Faraday's preference for clear, classical language won out over the fading 'condenser.'

The shift happened between 1850 and 1900 as electrical engineering formalized into a discipline. 'Condenser' lingered in British usage through the early 1900s, but 'capacitor' became standard in physics and electrical engineering textbooks. The name finally matched what the device actually does: it has the capacity to hold charge. The word itself holds the definition.

Every capacitor in every circuit board today carries that Latin etymology in its name—capax, able to hold. From the simplest capacitor in a transistor radio to the massive capacitor banks in power stations, the word hasn't changed in 150 years. Once the right word arrives, it sticks.