dung heap vs dunghill

dung heap

noun
  • A mound of animal droppings for agricultural use. 

dunghill

noun
  • A heap of dung, especially one for agricultural purposes. 

  • Any wretchedly mean, dirty or loathsome place, situation or condition. 

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