tiring vs untiring

tiring

adj
  • That tires or tire. 

noun
  • Bits of bone and tough organic material from a corpse given to hawks to abate their hunger. 

  • The action of tiring. 

untiring

adj
  • Not able to be tired; inexhaustible. 

  • Unfailing; resolute. 

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