late 14c., "writer of commentaries," agent noun in Latin form from comment or commentary (Latin commentator meant "inventor, author," in Late Latin "interpreter"). Meaning "writer of notes or expository comments" is from 1640s; sense of "one who gives commentary" (originally in sports) is from 1928. Related: Commentatorial.
"Well, Jem, what is a commentator?["]—"Why," was Jem's reply, "I suppose it must be the commonest of all taturs." ["Smart Sayings of Bright Children," collected by Howard Paul, 1886]
1610s, "one who revises" (a sense now obsolete), agent noun from review (v.). As "one who critically examines and passes judgment on new publications or productions; a writer of reviews," from 1650s.
"space-traveler," 1929 in scientific speculation, popularized from 1961 by U.S. space program, a compound from Greek elements, from astro- "star" + Greek nautes "sailor," from PIE root *nau- "boat." French astronautique (adj.) had been coined 1927 by "J.H. Rosny," pen name of Belgian-born science fiction writer Joseph Henri Honoré Boex, on model of aéronautique, and Astronaut was used in 1880 as the name of a fictional spaceship by English writer Percy Greg in "Across the Zodiac."