What was the term 'pop song' first used?

The term 'pop song' was first used in the late 1920s, originally as a shorthand for "popular song." It referred to music that was commercially successful and aimed at a broad audience, distinguishing it from more niche genres. By the 1950s, 'pop' became increasingly associated with the emerging rock and roll movement, further defining the genre as a staple of mainstream music.