furtive vs secret

furtive

adj
  • Of a thing: done with evasive or guilty secrecy. 

  • Of a thing: that has been acquired by theft; stolen; also (generally) taken stealthily. 

  • Of a person or an animal: sly, stealthy. 

  • Of a person, etc.: inclined to steal; pilfering, thieving. 

secret

adj
  • Being or kept hidden. 

noun
  • Private seclusion. 

  • A piece of knowledge that is hidden and intended to be kept hidden. 

  • The key or principle by which something is made clear; the knack. 

  • A form of steel skullcap. 

  • Something not understood or known. 

  • Any prayer spoken inaudibly and not aloud; especially, one of the prayers in the Tridentine Mass, immediately following the "orate, fratres", said inaudibly by the celebrant. 

verb
  • To make or keep secret. 

  • To hide secretly. 

How often have the words furtive and secret occurred in a corpus of books? (source: Google Ngram Viewer )