According to Grove Music Online, the term "pop music" "originated in Britain in the mid-1950s as a description for rock and roll and the new youth music styles that it influenced ...".
The Oxford Dictionary of Music states that while pop's "earlier meaning meant concerts appealing to a wide audience ... since the late 1950s, however, pop has had the special meaning of non-classical mus[ic], usually in the form of songs, performed by such artists as the Beatles, the Rolling Stones, ABBA, etc".