double-faced vs mendacious

double-faced

adj
  • deceitful; hypocritical; treacherous 

  • Having two functional faces. 

mendacious

adj
  • Lying, untruthful or dishonest. 

  • False or untrue. 

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