garbage collection vs street sweeper

garbage collection

noun
  • A service, generally run by local government, for transporting household garbage to the appropriate facility. 

  • An automatic mechanism that frees up resources (such as allocated memory) that are no longer in use. 

street sweeper

noun
  • A machine used to sweep streets. 

  • A person who is employed to sweep streets, pavements, and gutters, keeping them clear of litter. 

How often have the words garbage collection and street sweeper occurred in a corpus of books? (source: Google Ngram Viewer )