Why is a "cover version" so called?

Because it “covers” the same musical ground as the original? Something to do with the record cover itself? Or am I missing something obvious?

I always figured it was something along the lines of “Same song, different cover”, a sort of cynical joke that they may as well just sell the sleeve empty as you’ve already got the music.

How long has this term meant this? I’ve come across it only in the last year or so. I’m 42 now, so it seems pretty recent.

Not quite that recent. Among other meanings, my OED shows for the verb “cover”:

So it goes back to the early 1960’s at the very least. For myself, I’ve heard (and used) it for quite a while. It seems to me that I remember it in fairly common use in my high school days, which were the early 1970’s.

I think you’ll find it goes back at least to the 50’s. During the seminal days of rock and roll, white artists often made cover versions of rhythm and blues recordings done by black artists. This was in the days when some considered rock and roll a tool of the devil, and white parents were aghast at the mere thought of their darlings being influenced by those sinister colored folks.

Common sense tells me the term evolved from the verb cover in the general sense of taking care of or including something. As in, “there’s a cool song that we can’t play on our station because the artist is black, let’s get it performed by a white artist.” When that song was so recorded, it was covered.

As a college deejay,I know this has been around since the 50’s. The biggest culprits were Pat Boone, Georgia Gibbs, & the Crew Cuts. It was 99+& of the time whites stealing sales from blacks. Rarely did a black “cover " a white artist, but Otis Wiiliams & the Chams (black) covered Cathy Carr’s” Ivory Tower" & the Dubs covered the Skyliners. Unfortunately, the word has been misused so much that now it seems to mean remake. But at the time the Beatles REMADE Twist & Shout & Please Mr Postman etc etc, didn’t cover them. Cover meant to cover the market.
GaryT, above ,summarizes the reasons for it. BTW, the only cover generally believed to be better than the original was the Diamonds’ “Little Darlin’”(Original by the Gladiolas).