Why is it called “rock n’ roll?” What does the “roll” mean? Why is it sometimes “and” yet sometimes “n’?”

(Adapted from Dictionary.com)

Is “Rocket ‘88” by Jackie Brenston and his Delta Cats the very first rock and roll record? Musicologists have debated this for years.
Another equally hot topic: where does the term “rock and roll” actually come from?

• “Rock” comes from Old English roccain, related to Old Nordic rykkja, meaning “to pull, tear, or move.” One early recorded use in literature appears in the lullaby Rock-a-bye Baby from 1805.
• “Roll” stems from Latin rotula, meaning “small wheel.” The phrase “rocking and rolling” was used by 17th-century sailors to describe the motion of a ship at sea.

By the 1920s, “rocking and rolling” became a popular double entendre for either dancing or sex. Trixie Smith’s 1922 blues song My Man Rocks Me (With One Steady Roll) is one of the earliest uses of the phrase in music.

Later, Cleveland DJ Alan Freed popularized the term “rock and roll” on his radio show The Rock and Roll Session, blending rhythm and blues with country music. As his show grew in popularity, so did the phrase that defined an entire musical movement.

(And why is the “and” sometimes written as ‘n? That’s called apocopation—the omission of the final sound of a word.)