This Novena, or 9 days of prayer, was asked of Our Lord to the Apostles at His Ascension into Heaven.  This is the originator of the term and the 9 days of prayer known as a Novena.  It is a tradition within the Church to pray along with the Apostles for the coming Gifts of the Holy Spirit during these 9 days before Pentecost.  This Link will direct you to EWTN and the prayers for this Novena to the Holy Spirit.