grumble vs niggle

grumble

noun
  • A surly complaint. 

  • A low thundering, rumbling or growling sound. 

  • The sound made by a hungry stomach. 

verb
  • To utter in a grumbling fashion. 

  • To complain; to murmur or mutter with discontent; to make ill-natured complaints in a low voice and a surly manner. 

  • To make a low, growling or rumbling noise, like a hungry stomach or certain animals. 

niggle

noun
  • A minor complaint or problem. 

verb
  • To use, spend, or do in a petty or trifling manner. 

  • To dwell too much on minor points or on trifling details. 

  • To fidget, fiddle, be restless. 

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