bellow vs groaning

bellow

noun
  • The deep roar of a large animal, or any similar loud noise. 

verb
  • To shout in a deep voice. 

  • To make a loud, deep, hollow noise like the roar of an angry bull. 

groaning

noun
  • A low sound associated with extended suffering, sorrow, and toil. 

adj
  • Heavily laden, as if to creak under the strain. 

  • That groans. 

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