What's the "een" in Halloween?
"science of causes or causation," 1550s, from Late Latin aetiologia, from Greek aitiologia "statement of cause," from aitia "cause" + -logia "a speaking" (see -logy). Related: Etiologic; etiological.
etiology e·ti·ol·o·gy or ae·ti·ol·o·gy (ē'tē-ŏl'ə-jē)
The science and study of the causes or origins of disease.
The cause or origin of a disease or disorder as determined by medical diagnosis.