gluten n.

"viscous adhesive substance," early 13c., from Old French glu "glue, birdlime" (12c.), from Vulgar Latin *glutis or Late Latin glutem (nominative glus) "glue," from Latin gluten "glue, beeswax," from PIE *gleit- "to glue, paste" (source also of Lithuanian glitus "sticky," glitas "mucus;" Old English cliða "plaster"), from root *glei- "clay," also forming words with a sense of "to stick together" (see clay). Formerly also glew. In reference to glue from boiled animal hoofs and hides, c. 1400. Glue-sniffing attested from 1963.

blood-clotting substance, 1800, from Latin fibra "a fiber, filament" (see fiber) + chemical suffix -in (2). So called because it is deposited as a network of fibers that cause the blood to clot.