hairline vs rarefied

hairline

adj
  • very thin, as thin as a hair 

noun
  • A fishing line made from hair. 

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

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

  • A very thin fissure. 

rarefied

adj
  • Less dense than usual; thin. 

  • Distant from the lives and everyday concerns of ordinary people; esoteric, exclusive, select. 

  • Elevated in style or nature, sublime; of high intellectual or moral value. 

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