bombard vs field gun

bombard

noun
  • a medieval primitive cannon, used chiefly in sieges for throwing heavy stone balls. 

  • A bombardment. 

  • A bombardon. 

verb
  • To direct at a substance an intense stream of high-energy particles, usually sub-atomic or made of at most a few atoms. 

  • To attack something or someone by directing objects at them. 

  • To continuously attack something with bombs, artillery shells or other missiles or projectiles. 

  • To continuously send or direct (at someone) 

field gun

noun
  • An artillery piece, originally a smaller gun that could accompany a field army on the march and when in combat could be moved about the battlefield in response to changing circumstances. 

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