cold-blooded vs with straight face

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. 

with straight face

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