headgear vs top hat

headgear

noun
  • The lifting gear at the head of a mine or deep well. 

  • A type of orthodontic appliance attached to dental braces that aids in correcting severe bite problems. 

  • The harness that fits on a horse's head. 

  • Anything worn on the head, such as a hat, hood, helmet, etc. 

  • The rigging on the foresail. 

top hat

noun
  • A kind of steel batten. 

  • A man's formal hat, with a tall cylindrical crown (often of silk). 

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