hardened vs head-on

hardened

adj
  • Unfeeling; pitiless; callous. 

  • Inured; toughened. 

  • Firmly established or unlikely to change; inveterate. 

  • Having extra defences against attack; highly fortified. 

head-on

adj
  • Direct, abrupt, blunt or unequivocal; not prevaricating. 

  • Of a collision, from the front or in the direction of motion. 

noun
  • A collision from the front. 

adv
  • With the front of a vehicle. 

  • With direct confrontation. 

How often have the words hardened and head-on occurred in a corpus of books? (source: Google Ngram Viewer )