How come in English one talks about being able to "playback" media content, like music or movies, instead of just "play"? Why is -back added to the word? What is the origin of the expression?
The definition is given by Wiktionary to mean:
The replaying of previously recorded sound or moving images.
The reason -back was added, was because, this was a "replay" of a previously recorded media article.
The origin of the expression is from the phrase "play back" (which is different from "playback")
1925–30; noun use of verb phrase play back
"Play back" is defined as :
(idiomatic, transitive) To replay a recording.