double-faced vs perfidious

double-faced

adj
  • deceitful; hypocritical; treacherous 

  • Having two functional faces. 

perfidious

adj
  • Of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance. 

How often have the words double-faced and perfidious occurred in a corpus of books? (source: Google Ngram Viewer )