The Straight Dope: Who invented the term "rock 'n' roll"?
The term was first used to describe a particular kind of music.
In the 1920s the words "rock" and "roll," used separately or together, were employed by blacks to mean partying, carrying on, and/or having sex. According to rock historian Nick Tosches, blues singer Trixie Smith recorded a tune in 1922 called "My Daddy Rocks Me (With One Steady Roll)" for Black Swan Records. "Daddy," suffice it to say, was not trying to rock little Trixie to sleep.
That's why Rock music is so exciting :)