I don't see why there couldn't be more holy swords, or why anyone would even think that there aren't, but the Swords of The Cross are explicitly a set of three linked by the crucification and named after 1 Corinthians 13:13: "And now these three remain: faith, hope and love. But the greatest of these is love." (Text of New International Version Bible). Fidelacchius being the sword of Faith, Esperacchius the sword of Hope, and Amoracchius the sword of Love.