twin brother of Castor (q.v.), hence also the name of the beta star of Gemini (though slightly brighter than Castor), 1520s, from Latin, from Greek Polydeukēs, literally "very sweet," or "much sweet wine," from polys "much" (from PIE root *pele- (1) "to fill") + deukēs "sweet" (prom PIE *dleuk-; see glucose). The contraction of the name in Latin is perhaps via Etruscan [Klein].
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.