Is it ensure, insure, or assure?
late 13c., sugre, from Old French sucre "sugar" (12c.), from Medieval Latin succarum, from Arabic sukkar, from Persian shakar, from Sanskrit sharkara "ground or candied sugar," originally "grit, gravel" (cognate with Greek kroke "pebble"). The Arabic word also was borrowed in Italian (zucchero), Spanish (azucar), and German (Old High German zucura, German Zucker), and its forms are represented in most European languages (cf. Serb. cukar, Polish cukier, Russian sakhar).
Its Old World home was India (Alexander the Great's companions marveled at the "honey without bees") and it remained exotic in Europe until the Arabs began to cultivate it in Sicily and Spain; not until after the Crusades did it begin to rival honey as the West's sweetener. The Spaniards in the West Indies began raising sugar cane in 1506; first grown in Cuba 1523; first cultivated in Brazil 1532. The -g- in the English form cannot be accounted for. The pronunciation shift from s- to sh- is probably from the initial long vowel sound syu- (as in sure). Slang "euphemistic substitute for an imprecation" [OED] is attested from 1891. As a term of endearment, first recorded 1930. Sugar maple is from 1753. Sugar loaf was originally a moulded conical mass of refined sugar (early 15c.); they're now obsolete, but sense extended 17c. to hills, hats, etc. of that shape.
early 15c., "to sweeten with sugar," also figuratively, "to make more pleasing, mitigate the harshness of," from sugar (n.). Related: Sugared; sugaring.
sugar sug·ar (shug'ər)
A crystalline or powdered substance consisting of sucrose obtained mainly from sugar cane and sugar beets and used in many medicines to improve their taste.
Any of a class of water-soluble crystalline carbohydrates, including sucrose and lactose, having a characteristically sweet taste and classified as monosaccharides, disaccharides, and trisaccharides.
Any of a class of crystalline carbohydrates that are water-soluble, have a characteristic sweet taste, and are universally present in animals and plants. They are characterized by the many OH groups they contain. Sugars are monosaccharides or small oligosaccharides, and include sucrose, glucose, and lactose.