gang up on vs pile on

gang up on

verb
  • To join together in a group in order to overpower someone else. 

pile on

verb
  • To jump on top of someone or something quickly. 

  • To criticize someone or something in a concerted effort. 

  • To unnecessarily extend the margin of a winning score. 

noun
  • An argument or fight in which one side is greatly advantaged by being more numerous or more closely allied than the other side. 

How often have the words gang up on and pile on occurred in a corpus of books? (source: Google Ngram Viewer )