staunch vs undependable

staunch

noun
  • Synonym of afterdamp (“suffocating gases present in a coal mine after an explosion caused by firedamp”) 

adj
  • Strongly built; also, in good or strong condition. 

  • Not permitting water or some other liquid to escape or penetrate; watertight. 

  • Staying true to one's aims or principles; firm, resolute, unswerving. 

  • Dependable, loyal, reliable, trustworthy. 

  • Impermeable to air or other gases; airtight. 

  • Of a hunting dog: that can be depended on to pick up the scent of, or to mark, game. 

undependable

adj
  • Not dependable. 

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