AETIOLOGY or ETIOLOGY, strictly, science or philo sophy of causation, but generally used to denote the part of any special science (and especially of that of medicine and disease) which investigates the causes and origin of its phenomena. An aetiological myth is one which is regarded as having been in vented ex post facto to explain some fact, name, or coincidence, the true account or origin of which has been forgotten. Such myths were often based on grotesque philological analogies, ac cording to which an existing connection between two personalities (cities, etc.) was traced back to a common mythical origin. The preferred spelling of the word in the United States is Etiology.