hibernal vs piercing

hibernal

adj
  • Of or pertaining to winter; brumal or hiemal 

piercing

adj
  • Of sound, loud and sharp; shrill. 

  • Appearing to look deeply into; penetrating. 

  • Of temperature, extremely cold so that it penetrates through clothing and shelter. 

noun
  • A hole made in the body so that jewellery can be worn through it. 

  • An item of jewellery designed to be fitted through a piercing (sense 2). 

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