"I choose them as real men, of my name-Jacques is my name-to whom the sight is likely to do good..."
"My present name, though but slightly changed from my mother's, is not, as you will remember, my own. I wish to tell you what that is, and why I am in England."
"...By slow degrees the weight broke away the earth upon it, and came to the surface. Young Jerry knew very well what it would be; but, when he saw it, and saw his honored parent about to wrench it open, he was so frightened, being new to the sight..."
This quote reveals that Monsieur Defarge is secretly a revolutionary who knows and uses their secret code name. He even hosts other revolutionaries who use the same secret code name and shows them Dr. Manette, whom he was charged with taking care of.
Charles Darnay has been keeping his true name a secret from everybody he knows. by extension, he has also kept his family and heritage secret from all those around him.
In this quote, Jerry's son watches his dad dig up a grave after he said was going fishing. He kept his night-job as a grave robber secret from everybody except his partners in crime.
"Are you dying for him?' she whispered. 'And his wife and child. Hush! Yes.' 'Oh, you will let me hold your brave hand, stranger?' 'Of course my dear sister; to the last."
Dr. Manette kept his reason for imprisonment and his life prior to that hidden from everybody, except of course from those who knew him. not even the person closest to him after his imprisonment, his daughter, knew what happened until the letter was read.
Sydney Carton secretly disguises himself as Charles Darnay and takes his place in line for the guillotine where only a single person realizes he is not Darnay. He dies and Darnay lives, in secret.