Where did the term 'Rock and Roll' originate from?

What is the meaning of term 'Rock and Roll'? Where did it originate from?


I know it's a form of music that originated in 50s, I want to know how 'Rock' combined with 'Roll'?


Thnxs!!|||Rock-and-Roll (r盲k'n roll') n. first so used (1951) by Alan Freed, Cleveland disc jockey, taken from the song "My Baby Rocks Me with a Steady Roll". The use of rock, roll, rock and roll, etc., with reference to sexual intercourse, is traditional in blues, a form of popular music that evolved in the 1950's from rhythm and blues, characterized by the use of electric guitars, a strong rhythm with an accent on the offbeat, and youth-oriented lyrics. A form of popular music arising from and incorporating a variety of musical styles, especially rhythm and blues, country music, and gospel. Originating in the United States in the 1950s, it is characterized by electronically amplified instrumentation, a heavily accented beat, and relatively simple phrase structure|||I'm not sure but I think it's from the way the music made the people want to dance.But I'm not positive.