means A cleansing substance, usually made by combining fats or oils with an alkali, that lifts dirt and grease so they can be rinsed away with water.

from From Old English 'sāpe,' with cousins across the Germanic languages (German 'Seife,' Dutch 'zeep'). The Romans borrowed a related word as Latin 'sapo,' and Pliny the Elder claimed it was a Gallic invention of tallow and ash — though whether the Gauls used it for washing or, as he suggested, for reddening their hair, is part of the murk. The chemistry of grease meeting ash is ancient and probably stumbled upon many times over, but the word itself comes down to us from the north.