Good grief! This makes five words in a row where the word is an alternate spelling of the same word but with the leading “a” chopped of.
Aetiology, which is spelled etiology in the United States, is the study of the cause of things. In the field of medicine, aetiology (or etiology) is the causes or origins of a disease or abnormal condition.
I am Canadian. Our spellings are a mix of American and British spellings. Sometimes we use British spellings, like colour and centre, but sometimes we use American spellings, like organization and synchronize. I can’t tell you whether we use the British spelling, aetiology, or the American spelling, etiology, for this word.
I’d never heard or seen the word aetiology or etiology until now and I’ll probably never use it again. Under the circumstances, I’m way too lazy to look up the correct Canadian spelling when there is so little gain. As far as I’m concerned, my fellow Canadians can use whichever spelling they like. I’m probably done with the word.