etiology

etiology also aetiology [ˌitiˈɒlədʒi] n.

1.) The assignment of a cause, the rendering of a reason; also, the reason annexed, the wherefore of a command or utterance.
2.) The science or philosophy of causation; that part of philosophy which treats of the demonstration of causes; the part of any special science which speculates on the causes of its phenomena.
3.) That branch of medical science which investigates the causes and origin of diseases; the scientific exposition of the origin of any disease (O.E.D. 2nd Ed.).

Etymology: Adaptation of Latin ætiologia, from Greek αἰτιολογία, giving a cause: αἰτία cause, reason + -λογία discourse.

"It will start in the E.R., at the intake desk if C.T.'s late in following the ambulance, or in the green-tiled room after the room with the invasive digital machines; or, given this special M.D.-supplied ambulance, maybe on the ride itself: some blue-jawed M.D. scrubbed to an antiseptic glow with his name sewn in cursive on his white coat's breast pocket and a quality desk-set pen, wanting gurneyside Q&A, etiology and diagnosis by Socratic method, ordered and point by point" (Infinite Jest, David Foster Wallace, 1996).

(Greek Physician Galen Applying A Treatment Of Cupping, Robert Thom, 1959)