Ha! I like footnote #6, and I paraphrase: some guy living in Azusa quotes some other guy who’s godfather said it means “skunk hill” because of the skunks, the small polecat variety, on the hill named “Azuncsabit” by the Indians, east of the town where the ranch house of the grant stood.
You can download the PDF of the journal article here.
How cool is that? I wonder if anyone has mapped those place names. I shall have to buy that book and spent far too longer reading it than I have time for!