crowning vs hairline

crowning

noun
  • The stage of vaginal childbirth when the infant's head remains consistently visible at the vulva. 

  • A coronation. 

  • The act of one who crowns (in various senses). 

adj
  • Supreme; of a surpassing quality or quantity. 

hairline

noun
  • The line along one's forehead where hair starts growing. 

  • A fishing line made from hair. 

  • A very thin line in writing, drawing, or typography. 

  • A very thin fissure. 

adj
  • very thin, as thin as a hair 

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