pole-vault vs somersault

pole-vault

verb
  • To perform a pole vault 

  • To vault over something using a pole vault 

somersault

verb
  • To perform a 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. 

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