First used by Galen of Pergamon (129AD - 200AD) the word [etiology] is of Greek origin. [α?τία] or [aitia], meaning "cause", and [λογία] or [-ology], meaning "study of". Etiology is the "study of cause". In medicine this word I used to denote the study of the causes for a pathology, disease, or condition.

Because of its Greek origin, Skinner (1970) states that the proper way of spelling this term should be ?tiology, but the initial "a" has been discarded through use.

There are many pathologies of unknown origin. In this case the word to use would be [idiopathic] or [idiopathy] meaning "of unknown cause"