Songfacts®:

• Bell-bottoms are trousers which are short at the top and wide at the bottom. Traditionally part of a sailor's uniform, they became fashionable attire in the mid-1960s for the young in America and Europe. The allusion is to a bell-mouth.
  
  So what has this to do with this song? Well, the song title, literally meaning "trumpet trousers," is the Korean name for bell-bottoms.
• Other singers who have recorded songs titled after the flared trousers include:
  
  British radio and TV singing star, Alma Cogan, who made her breakthrough in 1954 with the Hal David song "Bell Bottom Blues." The biggest hit version in the United States was recorded by Teresa Brewer.
  
  Sixteen years later, Derek & The Dominos recorded an entirely different song also titled "Bell Bottom Blues" for their Layla And Other Assorted Love Songs album.
• As expected, the video is filled with loads of bell bottom trousers. It also includes a new dance move when Psy sings the hook (following the dances in "Gangnam Style" and "Gentleman"). In this instance he holds one arm out while the other one punches to the beat. It's very similar to the move from T-ara's "Roly Poly" 2011 single, which was a huge, disco-inspired hit in Korea.