Gloss as a noun meaning "shine," or as part of the phrase gloss over, meaning "to treat or describe (something) as if it were not important," but those uses are unrelated to the modern meaning of gloss.
Gloss comes from the noun gloss that refers primarily to a brief explanation. It is Greek in origin, coming from glossa or glotta, meaning "tongue," "language," or "obscure word."
Glossary is from this same root, as are two anatomical terms: glottis refers to the elongated space between the vocal cords and also to the structures that surround this space; epiglottis refers to the thin plate of flexible cartilage in front of the glottis that folds back over and protects the glottis during swallowing.
