satelliteyoudaoicibaDictYouDict
satellite: [16] Satellite comes via French satellite from Latin satelles ‘attendant, escort’, which itself probably went back to Etruscan satnal. Its use for a ‘body orbiting a planet’ is first recorded in English in 1665, and comes from the astronomer Johannes Kepler’s application of Latin satelles to the moons of Jupiter.
sputnikyoudaoicibaDictYouDict
sputnik: [20] Russian sputnik means literally ‘travelling companion’ (it is formed from s ‘with’ and put ‘way, journey’, with the agent suffix -nik). The Soviets gave the name to the series of Earth-orbiting satellites that they launched between 1957 and 1961. The first bleeps from space in October 1957 came as a severe shock to the West, which had not thought Soviet science capable of such a thing, and immediately propelled sputnik into the English language (the politically charged English version ‘fellow traveller’, which is more strictly a translation of Russian popútchik, was tried for a time, but never caught on).

It became one of the ‘in’ words of the late 1950s, and did much to popularize the suffix -nik in English (as in beatnik and peacenik).
orbit (v.)youdaoicibaDictYouDict
1946, from orbit (n.). Related: Orbited; orbiting.
satellite (n.)youdaoicibaDictYouDict
1540s, "follower or attendant of a superior person," from Middle French satellite (14c.), from Latin satellitem (nominative satelles) "attendant, companion, courtier, accomplice, assistant," perhaps from Etruscan satnal (Klein), or a compound of roots *satro- "full, enough" + *leit- "to go" (Tucker); compare English follow, which is constructed of similar roots.

Meaning "planet that revolves about a larger one" first attested 1660s, in reference to the moons of Jupiter, from Latin satellites, which was used in this sense 1610s by German astronomer Johannes Kepler (1571-1630). Galileo, who had discovered them, called them Sidera Medicæa in honor of the Medici family. Meaning "man-made machinery orbiting the Earth" first recorded 1936 as theory, 1957 as fact. Meaning "country dependent and subservient to another" is recorded from 1800.
periastronyoudaoicibaDictYouDict
"The point nearest to a star in the path of a body orbiting that star", Mid 19th century: from peri- 'around' + Greek astron 'star', on the pattern of perigee and perihelion.
apastronyoudaoicibaDictYouDict
"The point in the path of a celestial object orbiting a star at which it is farthest from the star", Mid 19th cent.; earliest use found in William H. Smyth (1788–1865), naval officer and surveyor. From apo- + ancient Greek ἄστρον star, after aphelion.