Whale tail

When women dress up in a G-string, which is partly visible under their trousers, this is called a whale tail. Female celebrities such as Christina Aguilera, Victoria Beckham, Mariah Carey, Paris Hilton and Britney Spears, made displaying whale tails popular in the early 2000s. Low-rise jeans and thong panties became popular at the same time 
Low-waisted trousers, such as low-rise jeans or hip-huggers, and higher-cut thongs led to greater exposure of the whale tail. The trend was also associated with the trend of sporting lower back tattoos.