Meaning

noun an expert who observes and comments on something

noun a writer who reports and analyzes events of the day

originIn form, from Middle English commentator, from Latin commentātor (“author, inventor, interpreter, jailer”), from commentātus + -or (“-er: forming agent nouns”), from commentāri (“to ponder, to study, to write upon”), from comminīscor (“to think over, to invent”) + -tārī (“to frequently be ~ed”). In meaning, influenced by comment and commentary. By surface analysis, comment + -ator.

Etymology from Wiktionary, CC BY-SA 3.0