eat away at vs irritate

eat away at

verb
  • To cause to feel uneasy, troubled, worried, guilty, or vexed; to bother about something. 

  • To erode. 

  • To consume or use up, erode or wear away gradually. 

irritate

verb
  • To provoke impatience, anger, or displeasure in. 

  • To cause or induce displeasure or irritation. 

  • To induce pain in (all or part of a body or organism). 

How often have the words eat away at and irritate occurred in a corpus of books? (source: Google Ngram Viewer )