Where does the word "satellite" come from?

Before it was a moon or a machine, a satellite was a man who walked behind someone important. The orbit came later.

The Latin satelles meant an attendant on a distinguished person: a bodyguard, a courtier or an assistant. Etymonline notes that in Cicero the word often had a bad sense, "an accomplice" in a crime. Where the Latin word came from is unknown. One suggestion links it to Etruscan, but that is only a proposal.

English took it partly through Middle French, where satellite meant a bodyguard. Merriam-Webster dates the English word to about 1520. Word Origins finds an early English use in 1522, in Alexander Barclay's translation of Sallust, describing a "treatoure satellyte" who broke into a house. Etymonline dates the sense of a follower to the 1540s, though it was rare before the late 1700s.

The astronomical sense came from Johannes Kepler. In 1610 Galileo found four moons circling Jupiter. Following his secretary's advice, he called them the Medicean stars, in honor of the Medici family. Kepler called them satellites instead. The image fit: small bodies attending a great planet, like guards around a prince.

Sources differ on Kepler's first use. Wikipedia points to his 1610 pamphlet on the "four satellites" of Jupiter. Word Origins cites his Latin Dioptrice of 1611. Etymonline simply says the 1610s.

Kepler's singular form was satellitium, which suggests a whole retinue rather than one servant. In the Dioptrice he was also speaking in Galileo's voice, not claiming the discovery. Word Origins knows of no case where Galileo himself used the word for the moons.

English followed. In 1640 a court pageant for Charles I announced that "JUPITER also commeth back again with his Satellites." Etymonline dates the general sense of a body circling a larger one to the 1660s.

The courtly meaning never fully disappeared. By 1800 a dependent country could be called a satellite. Word Origins cites a 1780 London letter calling some territories "the Appendages, or Satellites of America."

Fiction then put machines in the sky. Jules Verne's 1879 novel The Begum's Fortune imagined a projectile fired from a cannon into orbit, becoming "a second satellite" of the earth. Etymonline records the man-made sense by 1936 as a theory. It became fact in October 1957, with the Soviet launch of Sputnik.