Jennifer Viegas at Discovery has an excellent piece on first use of the term Rock-N-Roll and the first Rock-N-Roll song.
“That’s All Right Mama” by Arthur “Big Boy” Crudup is the world’s oldest rock and roll song, according to Southeastern Louisiana University rock historian Joseph Burns, who also thinks this song could contain the first ever guitar solo break.
But more importantly, we can thank the maritime tradition for the term itself
It started as a nautical phrase meaning the movement of the boat up and down and back and forth,” Burns said. “Sometime in the late 1800s to early 1900s, gospel and jubilee music co-opted the term and used it to mean being rocked and rolled in the arms of the Lord. In fact, the first recorded use of the term in a song was ‘Camp Meeting Jubilee’ in 1916.”