cold fish vs cold-blooded

cold fish

noun
  • A heartless individual; a person lacking empathy and emotion. 

  • A sexual partner who, during sex, lacks vigor or emotional reciprocity. 

cold-blooded

adj
  • Of a type of horse: tall and muscular, usually good-natured and suitable for heavy work. 

  • Lacking emotion or compunction. 

  • Having an unregulated body temperature; ectothermic. 

How often have the words cold fish and cold-blooded occurred in a corpus of books? (source: Google Ngram Viewer )