facial hair vs five o'clock shadow

facial hair

noun
  • Hair on the face of a human, such as the eyebrows of a man or woman or the androgenic hair (beard or moustache) of a man. 

  • Hair on the face of an animal. 

five o'clock shadow

noun
  • A beard growth visible late in the day on the face of a man with facial hair growth that was clean-shaven in the morning. 

How often have the words facial hair and five o'clock shadow occurred in a corpus of books? (source: Google Ngram Viewer )