double-faced vs sly

double-faced

adj
  • deceitful; hypocritical; treacherous 

  • Having two functional faces. 

sly

adj
  • Artfully cunning; secretly mischievous; wily. 

  • Done with, and marked by, artful and dexterous secrecy; subtle 

  • Light or delicate; slight; thin. 

  • Dexterous in performing an action, so as to escape notice 

adv
  • Slyly. 

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