keratin

Long before laboratories had names for proteins, people had a very practical word for the material in a ram’s horn: Greek kéras, “horn.” In the nineteenth century, scientists turned that ancient object-word into German Keratin, then English keratin, naming the stubborn substance that makes hair, nails, feathers, claws, hooves, and horns resist water and wear. Wait, really? The shiny crescent on your fingertip and the dramatic horn of a rhinoceros are built from variations on the same tough biological material. The same Greek root also traveled into carat, because ancient measures of precious stones were associated with horn-shaped or horn-related units—a linguistic doublet rather than a biological connection to nails. Whenever you see keratin, picture a Greek horn being carried into a modern laboratory: the old word survived by changing from an object into its hidden material.