mudflap vs wheel arch

mudflap

noun
  • A rectangular flap mounted near the wheel of a truck to prevent mud from being thrown up onto the vehicle. 

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 mudflap and wheel arch occurred in a corpus of books? (source: Google Ngram Viewer )