sphere

1530s, restored spelling of Middle English spere (c.1300) "space, conceived as a hollow globe about the world," from Old French espere (13c.), from Latin sphaera "globe, ball, celestial sphere," from Greek sphaira "globe, ball," of unknown origin.

Sense of "ball, body of globular form" is from late 14c. Medieval astronomical meaning "one of the 8 (later 10) concentric, transparent, hollow globes believed to revolve around the earth and carry the heavenly bodies" is from late 14c.; the supposed harmonious sound they made rubbing against one another was the music of the spheres (late 14c.). Meaning "range of something" is first recorded c.1600 (e.g. sphere of influence, 1885, originally in reference to Anglo-German colonial rivalry in Africa). A spherical number (1640s) is one whose powers always terminate in the same digit as the number itself (5,6, and 10 are the only ones).