The title makes a reference to Papillon, a book by Henry Charrière. Emmi mentions the seventh wave when she is on holiday in the Canary Islands. Papillon is an autobiography written by Henri Charrière, first published in France on 30 April 1969. Papillon is Charrière’s nickname, deriving from a butterfly tattoo inscribed on his chest. The novel details Papillon’s incarceration and subsequent escape from the French penal colony of French Guiana, and covers a 14-year period between 1931 and 1945. Papillon studied the waters and discovered possibilities at a rocky inlet surrounded by a high cliff. He noticed that every seventh wave was large enough to carry a floating object far enough out into the sea that it would drift toward the mainland.