den vs pothole

den

noun
  • A small cavern or hollow place in the side of a hill, or among rocks; especially, a cave used by a wild animal for shelter or concealment. 

  • Synonym of fort (“structure improvised from furniture, etc. for playing games.”) 

  • A comfortable room not used for formal entertaining. 

  • A group of Cub Scouts of the same age who work on projects together. 

  • A squalid or wretched place; a haunt. 

verb
  • To ensconce or hide oneself in (or as in) a den. 

pothole

noun
  • A vertical cave system, often found in limestone. 

  • A shallow pit or other edged depression in a road's surface, especially when caused by erosion by weather or traffic. 

  • A pit formed in the bed of a turbulent stream. 

  • A pit resulting from unauthorized excavation by treasure hunters or vandals. 

  • A shallow hole dug for the purpose of prospecting for opal or gold. 

  • A hole or recess on the top of a stove into which a pot may be placed. 

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