Is it ensure, insure, or assure?
late 14c., "soda ash," from Medieval Latin alkali, from Arabic al-qaliy "the ashes, burnt ashes" (of saltwort, a plant growing in alkaline soils), from qala "to roast in a pan." The modern chemistry sense is from 1813.
alkali al·ka·li (āl'kə-lī')
n. pl. al·ka·lis
A carbonate or hydroxide of an alkali metal, the aqueous solution of which is bitter, slippery, caustic, and characteristically basic in reactions.
Any of various soluble mineral salts found in natural water and arid soils.