potash (Dutch > New Latin: potassium carbonate).
Potassium carbonate was originally obtained by burning wood or other vegetable matter, soaking the ashes in water, and evaporating the resulting liquid in iron pots. The resulting substance was hence called potasschen in early Dutch, literally "pot ashes", and the word was adopted into English as potash. From it, or its French relative potasse, the chemist, Sir Humphry Davy, coined in 1807 the term potassium for the metallic element that occurs in potash.
Potash has been used in soap, fertilizers, etc. Potassium, a soft, silver-white, waxlike metallic chemical element, oxidizes rapidly when exposed to air. It occurs abundantly in nature in the form of its salts, which are used in fertilizers, glass, etc. The chemical symbol is K.
Potassium occurs in nature only in compounds and is essential for the growth of plants. It is one of the most abundant elements in the earth's crust, is the lightest metal known except lithium, and it belongs to the alkali metals.
Among potassium's most important compounds is potassium carbonate, commonly called "potash", and potassium nitrate, commonly called "saltpeter". Saltpeter is a borrowing of Old Middle English salpetre [about A.D. 1300]; a borrowing of Old French, salpetre, a learned borrowing from Medieval Latin; also borrowed directly from Medieval Latin sal petrae, "salt of rock"; (Latin sal, "salt" + petrae, genitive of Latin petra, "rock").