From the book’s pattern description:

"Cache-Coeur (rhymes with wash-her) literally translates from French as "hide the heart" and is used in the French dance world to describe the crossover tops ballerinas wear.  Designer Veronik Avery, who is French-Canadian, borrowed the romantic term for this short vest that, she says, both hides and warms the heart…Bergamo is the name of the tubular wool ribbon with which the vest is made."