mud flap vs scrote

mud flap

noun
  • A flap that hangs down behind a vehicle's wheel so that mud and other things kicked up by the wheel will hit the flap instead of a vehicle behind. 

scrote

noun
  • A worthless or contemptible person; a gobshite or toerag. 

  • The scrotum. 

  • A stereotypical low-value and obnoxious man. 

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