Source : Webster's Revised Unabridged Dictionary (1913)

AEtiology \[AE]`ti*ol"o*gy\, n. [L. aetologia, Gr. ?; ? cause +
   ? description: cf. F. ['e]tiologie.]
   1. The science, doctrine, or demonstration of causes; esp.,
      the investigation of the causes of any disease; the
      science of the origin and development of things.

   2. The assignment of a cause.

Source : WordNet®

aetiology
     n 1: the cause of a disease [syn: {etiology}]
     2: the philosophical study of causation [syn: {etiology}]