craven vs strong-willed

craven

adj
  • Unwilling to fight; lacking even the rudiments of courage; extremely cowardly. 

noun
  • A coward. 

verb
  • To make craven. 

strong-willed

adj
  • Having a vigorous, independent will 

How often have the words craven and strong-willed occurred in a corpus of books? (source: Google Ngram Viewer )