horseback riding vs riding

horseback riding

riding

noun
  • The behaviour in the motion of a vehicle, such as oscillation. 

  • A path cut through woodland. 

  • The act of one who rides; a mounted excursion. 

  • Electoral district or constituency. 

  • Any of the three administrative divisions of Yorkshire and some other northern counties of England. 

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