WebCause (medicine) Cause, also known as etiology ( / iːtiˈɒlədʒi /) and aetiology, is the reason or origination of something. [1] The word etiology is derived from the Greek αἰτιολογία, aitiologia, "giving a reason for" ( αἰτία, aitia, "cause"; and -λογία, -logia ). [2]