attack dog vs oppressor

attack dog

noun
  • A person who engages in rhetorical attacks on behalf of another. 

  • A dog used in the bloodsport of dogfighting. 

  • A person who fights physically on behalf of another. 

  • Any dog bred, trained or used for the purpose of attacking a target, either on command or on sight; trained either as a specialized form of police dog or a security force dog. 

oppressor

noun
  • Someone who oppresses another or others. 

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