It is so called because its oldest known manuscript was bought for the abbey of Santa Croce Avellana by St. Peter Damian (died 1073), probably dates from the middle of the sixth century. It follows neither chronological nor logical order, and seems to have grown to its present shape according as the compiler met with the materials that he has transmitted to us. Nevertheless, Girolamo Ballerini and Pietro Ballerini pronounce it a valuable collection because of the great number of early canonical documents (nearly 200) that are found in no other collection.