back alley vs curtilage

back alley

noun
  • An alleyway that runs behind a row of houses, or between rows of houses 

  • The anus. 

curtilage

noun
  • The area immediately surrounding a house, especially dooryard areas and sometimes including closely associated buildings and structures. 

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