atlas
book of maps
Today this word meansA bound book of maps. In anatomy, the first neck vertebra, which supports the head.
In 1595 the mapmaker Mercator put Atlas, bearer of the heavens, on the cover of his collection of maps.
The book sold widely, and "atlas" came to mean a book of maps — a book's title turned common noun.
The first vertebra, the one that carries the head, is called the atlas from the same image of holding aloft.