nom de voyage

…it shows that she is sore upon some point, and we are almost tempted to fear she is angry that her title of My Lady has not proved to her as good a nom de voyage in England as it has done in France…

His nom de voyage is Mr. Von Natas (which, it will be noticed, is his more familiar name read backwards.)

… But I beg your pardon, Eccellenza; I meant to say, that the person who sent you here should have told you my nom de voyage.—Gitano, I call myself.