eat away at vs get under someone's skin

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. 

get under someone's skin

verb
  • To irritate someone. 

  • To make a memorable impression or have a strong effect on someone; to impact someone's feelings, especially when such an effect is not expected or wanted. 

How often have the words eat away at and get under someone's skin occurred in a corpus of books? (source: Google Ngram Viewer )