glycogen n.

before vowels glyc-, word-forming element meaning "sweet," from Latinized combining form of Greek glykys, glykeros "sweet" (see gluco-). Used in reference to sugars generally. OED says a regular formation would be glycy-.

word-forming element technically meaning "something produced," but mainly, in modern use, "thing that produces or causes," from French -gène (18c.), from Greek -genes "born of, produced by," which is from the same source as genos "birth," genea "race, family," from PIE root *gene- "give birth, beget," with derivatives referring to procreation and familial and tribal groups. First used in late 18th century French chemistry (see oxygen), it probably involves a misunderstanding of -genes, as though it meant "that which produces."

1856, from French; see glycogen + -ic.