The Collaborative International Dictionary of English v.0.48:

Theogony \The*og"o*ny\, n. [L. theogonia, Gr. ?; ? a god + the
   root of ? to be born. See Theism, and Genus.]
   The generation or genealogy of the gods; that branch of
   heathen theology which deals with the origin and descent of
   the deities; also, a poem treating of such genealogies; as,
   the Theogony of Hesiod.
   [1913 Webster]

WordNet (r) 3.0 (2006):

theogony
    n 1: the study of the origins and genealogy of the gods