What is the origin of the saying 'The Painted Veil'?

Answer 1

It comes from the classic novel by W. Somerset Maugham.
“The Painted Veil” is a love story set in the 1920s that tells the story of a young English couple, Walter, a middle class doctor and Kitty, an upper-class woman, who get married for the wrong reasons and relocate to Shanghai, where she falls in love with someone else. When he uncovers her infidelity, in an act of vengeance, he accepts a job in a remote village in China ravaged by a deadly epidemic, and takes her along. Their journey brings meaning to their relationship and gives them purpose in one of the most remote and beautiful places on earth.