The story
From rock (move back and forth) + and + roll; originally a verb phrase common among African Americans, meaning "to have sexual intercourse"; it was a euphemism that appeared in song titles since at least 1914 (Trixie Smith's "My Man Rocks Me With One Steady Roll"). As a name for a specific style of popular music from the early 1950s, popularized by disc jockey Alan Freed in reference to the euphemistic use in song titles.
Etymology from Wiktionary, CC BY-SA 4.0.