κάθοδος

Electricity baffled early scientists who needed precise language for their experiments. When Michael Faraday began studying electrolysis in the 1830s, he realized that current seemed to flow in specific directions through substances. But the vocabulary didn't exist. The negative pole needed a name.

Faraday asked William Whewell, a Cambridge physicist and etymologist, to help. Whewell looked to Greek. Kathodos meant 'way down'—kata (down) plus hodos (way, path). In March 1834, Whewell proposed cathode for the negative terminal where current enters or exits a cell. The coining was deliberate, named, and dated.

Whewell gave Faraday three words in that same correspondence: cathode, anode (the way up), and electrode (the amber path—from elektron). All three followed the Greek metaphor of current as a flow with direction. All three were needed before electrical science could move forward.

Today we use cathode without thinking about the path it names. Cathode ray tubes created television. Cathodes power batteries. The word is invisible machinery—you never see it unless you're naming something electrical. That's the mark of a naming that worked.