commentator (n.)

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]