backflip vs somersault

backflip

noun
  • An act of rotating one's body 360 degrees in the backward direction. 

  • a total reversal in policy or opinion; a volte-face, a U-turn. 

verb
  • To perform a backflip (rotation of body). 

  • To completely reverse a policy or opinion; perform a U-turn. 

somersault

noun
  • Starting on one's feet, an instance of rotating one's body 360 degree while airborne or on the ground, with one's feet passing over one's head. 

verb
  • To perform a somersault. 

How often have the words backflip and somersault occurred in a corpus of books? (source: Google Ngram Viewer )