Potash

Potash /ˈpɒtæʃ/ is any of various mined and manufactured salts that contain potassium in water-soluble form. The name derives from pot ash, which refers to plant ashes soaked in water in a pot, the primary means of manufacturing the product before the industrial era. The word potassium is derived from potash.

Potash is produced worldwide at amounts exceeding 30 million tonnes per year, mostly for use in fertilizers. Various types of fertilizer-potash thus constitute the single largest global industrial use of the element potassium. Potassium was first derived by electrolysis of caustic potash (a.k.a. potassium hydroxide), in 1807.

Potash refers to potassium compounds and potassium-bearing materials, the most common being potassium chloride (KCl). The term potash comes from the Middle Dutch word potaschen (pot ashes, 1477).
The old method of making potassium carbonate (K
2CO
3) was by collecting or producing wood ash (an occupation carried out by ash burners), leaching the ashes and then evaporating the resulting solution in large iron pots, leaving a white residue called pot ash. Approximately 10% by weight of common wood ash can be recovered as pot ash. Later, potash became the term widely applied to naturally occurring potassium salts and the commercial product derived from them.

...
Wikipedia