/dɪsˈtʃɑːrdʒ/
[verb] To release someone or something from a duty, container, or place of confinement; to let out or send away. It can also mean to fire a weapon or to release a liquid or gas.
This word literally means 'to unload a cart' — a medieval image buried inside a word we now use for firing guns and leaving hospitals.
The word 'discharge' arrives in English in the 14th century, carried directly from Old French 'deschargier', which was a compound built from the prefix 'des-' (meaning 'away' or 'removal') and 'chargier', meaning 'to load' or 'to burden'. That root 'chargier' came from Late Latin 'carricare', which meant 'to load a cart or wagon', derived in turn from 'carrus', a Gaulish or Celtic word for a wheeled vehicle. So the earliest ancestor of 'discharge' is essentially a picture of someone heaving goods onto a cart — and to discharge something was to do the opposite: to unload it.
Late Latin 'carricare' also travelled in other directions across the Romance languages, giving us the English word 'charge' itself (via Old French 'chargier' → Middle English 'chargen'), as well as 'cargo' (via Spanish 'cargar' → 'cargo') and 'career' in one of its older senses relating to a road or track along which vehicles moved. Even the word 'car' connects back to that ancient Gaulish 'carrus'. This family of words is essentially the history of carrying things from place to place, encoded in language.
When 'discharge' entered Middle English, its earliest uses were very physical and practical. To discharge a ship meant to unload its cargo at port. To discharge a debt meant to remove the weight of what you owed — clearing the burden, just as one cleared a wagon. The metaphor of weight and its removal was central to all early uses, and you can still hear it faintly when someone says they have discharged their responsibilities, as if they have set down something heavy they were carrying.
From the 15th century onward, the word expanded into military language. A weapon could be 'discharged' — the shot or arrow released, the tension in the bow or the powder in a cannon suddenly unleashed. This use mirrors the original sense beautifully: a loaded weapon is charged, a fired one is discharged, the burden gone in a flash. By the 16th and 17th centuries, the word had spread further still — into medicine, where patients were discharged from care, and into law, where obligations, prisoners, and verdicts could all be discharged.
The electrical sense of 'discharge' — as in a battery or a bolt of lightning — came later, in the 18th century, as scientists began borrowing everyday language to describe the new mysteries of electricity. A capacitor or a storm cloud could be thought of as 'charged' with energy, and when that energy released all at once, it discharged. The metaphor of loading and unloading proved so flexible and intuitive that it moved seamlessly from medieval carts to the frontiers of physics, which is a remarkable journey for any single word to make.