shitbox vs winter rat

shitbox

noun
  • An old and decrepit automobile. 

  • A contemptible person. 

  • A dump; a run-down, messy or disgusting item. 

winter rat

noun
  • An old, unattractive automobile, purchased for little money, to be driven during brutal Great Lakes winters while the owner's "good" car remains garaged and protected from corrosive road salt for the season. 

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