mudguard vs wheel arch

mudguard

noun
  • A cover over the wheels of a vehicle, or a flap behind that wheel, to prevent water and mud being projected. 

wheel arch

noun
  • The shaped part of the bodywork of a car or other vehicle that allows the wheel to be accessed, and in the case of front wheels, enable them to be steered. 

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