aetiology

n. study of the causes of disease, etiology

Etiology (alternately aetiology, aitiology) is the study of causation. Derived from the Greek , "giving a reason for" ( "cause" + ). The word is most commonly used in medical and philosophical theories, where it is used to refer to the study of why things occur, or even the reasons behind the way that things act, and is used in philosophy, physics, psychology, government, and medicine, and biology in reference to the causes of various phenomena. An etiological myth is a myth intended to explain a name or create a mythic history for a place or family.
See more at Wikipedia.org...

Noun
1. the cause of a disease
(synonym) etiology
(hypernym) cause
2. the philosophical study of causation
(synonym) etiology
(hypernym) philosophy

(n.)
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.
  

(n.)
The assignment of a cause.
  

noun
(study of) the cause or origin of a disease