Now, no one is pretending this is an easy look to pull off, but whereas the whale tail was shaming because it was a fail – the byproduct of you scrabbling in the bottom of your bag for your Oyster card – the underbum is at least bold and brazen, in a lollipoppy, Katy Perry or Rihanna kind of a way.
They’ve always been a big hit at the box office: ethnically diverse, incredibly loyal, keen wearers of white vests (for the men) and underbum-showcasing hotpants (for the ladies).
"The denim hotpants with the underbum cleavage was a big look this summer but with the jeans you're getting a little more coverage.
2018, Catherine Keane, "Fashion must haves for Festival Season", Connect (Country Kerry), August 2018, page 18:
One of the more unfortunate fashion trends in my opinion of late has been the 'underbum' - ie, baring faintly obscene amounts of your rear end with festival-goers been[sic] the worst offenders.