Meaning

noun any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water

noun a mixture of soluble salts found in arid soils and some bodies of water; detrimental to agriculture

originFrom French alcali, from Medieval Latin alcali, ultimately from Arabic اَلْقِلْي (al-qily, “alkali, ashes of the saltwort”), related to قَلَى (qalā, “to roast in a pan, fry”).

Etymology from Wiktionary, CC BY-SA 3.0