King of Mauritania in Africa, fabled to have supported the world upon his shoulders. Of course, the tale is merely a poetical way of saying that the Atlas mountains prop up the heavens, because they are so lofty. We call a book of maps an “Atlas,” because it contains or holds the world. The word was first employed in this sense by Mercator, and the title-page of his collection of maps had the figure of Atlas with the world on his back.
Bid Atlas, propping heaven, as poets feign, His subterranean wonders spread!
Thomsom: Autumn, 797–8.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894