feckless vs increditable

feckless

adj
  • Lacking the courage to act in any meaningful way. 

  • Without skill, ineffective, incompetent. 

  • Lacking purpose. 

increditable

adj
  • Incapable of being believed; not creditable. 

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