pommel horse vs rocking horse

pommel horse

noun
  • An athletic event in which the pommel horse is used. 

  • An apparatus for gymnastic exercises with a cylindrical body covered with leather and two upright pommels, as hand grips, near the centre; held upright with adjustable legs. 

rocking horse

noun
  • a child’s toy consisting of a (usually wooden) horse mounted on a rocker or swing 

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