balancer vs head collar

balancer

noun
  • An acrobat. 

  • One who, or that which, balances. 

  • Any of the rear wings of certain insects used for stability in flight. 

head collar

noun
  • A halter for a horse 

  • A collar that fits around the neck and head 

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