also aetiology, "science of causes or causation," 1550s, from Late Latin aetiologia, from Greek aitiologia "statement of cause," from aitia "cause, responsibility" (from PIE *ai-t-ya-, from root *ai- (1) "to give, allot;" see diet, n.1) + -logia "a speaking" (see -logy). Related: Etiologic; etiological.