This question was asked in my dental school class:
What is the etiology of the diagnosis of the brain abscess? The original cause was an infected tooth which led to the proliferation of a certain bacteria which led to a brain abscess.
So how far back does the word etiology imply? Is the correct answer the infected tooth or the bacteria? Because bacteria was the direct cause of the brain abscess, but the infected tooth was the original cause of the bacteria's proliferation!
I believe the answer is the bacteria because that was the direct cause of the abscess but I would like the opinion of the literary wizards on this wonderful site.