before vowels, gluc-, word-forming element used since c. 1880s, a later form of glyco-, from Greek glykys "sweet," figuratively "delightful; dear; simple, silly," from *glku-, a dissimilation in Greek from PIE root *dlk-u- "sweet" (source also of Latin dulcis). De Vaan writes that "It is likely that we are dealing with a common borrowing from an unknown source." Now usually with reference to glucose.

also glycerine, thick, colorless syrup, 1838, from French glycérine, coined by French chemist Michel-Eugène Chevreul (1786-1889), from glycero- "sweet" (see glyco-) + chemical ending -ine (2). So called for its sweet taste. Still in popular use, but in chemistry the substance now is known as glycerol.