The Collaborative International Dictionary of English v.0.48:

Hymnology \Hym*nol"o*gy\, n. [Gr. ? hymn + -logy: cf. F.
   hymnologie.]
   1. The hymns or sacred lyrics composed by authors of a
      particular country or period; as, the hymnology of the
      eighteenth century; also, the collective body of hymns
      used by any particular church or religious body; as, the
      Anglican hymnology.
      [1913 Webster]

   2. A knowledge of hymns; a treatise on hymns.
      [1913 Webster]