hairline vs robust

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. 

robust

adj
  • Sensible (of intellect etc.); straightforward, not given to or confused by uncertainty or subtlety. 

  • Designed or evolved in such a way as to be resistant to total failure despite partial damage. 

  • Not greatly influenced by errors in assumptions about the distribution of sample errors. 

  • Resistant or impervious to failure regardless of user input or unexpected conditions. 

  • Requiring strength or vigor. 

  • Of an individual or skeletal element: strongly built; muscular; not gracile. 

  • Violent; rough; rude. 

  • Evincing strength and health; strong; (often, especially) both large and healthy. 

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