A song you didn't realize was a cover?

For a long time, I didn't know that Aretha's version was a cover. I had always thought hers was the original version until I found out the original version was by Otis Redding, who wrote the song. Here's an Otis Redding quote about it: "This is a song that a girl took away from me. A good friend of mine, this girl, she just took the song." Of course, we all know who he meant by "this girl".