I was looking for a source for Mowan as an Aboriginal name beyond the "usual suspects" i.e. "baby names" websites that mostly only blindly copy from each other, and was near giving up when I stumbled upon the following:
1917/1918 a German language scientist wrote a paper about various Aboriginal languages, in German. The paper is online here (however, only available with an account):
http://www.jstor.org/stable/40442927
And there they are, on page 459, two words in the language of the Aborigines living on the Cobourg peninsula, "inner dialect" (as opposed to "outer dialect"): "mowan" and "manif", both meaning "sun".
That's the peninsula, it seems:
https://en.wikipedia.org/wiki/Cobourg_Peninsula
What is this worth? Hard to say. Searching for Mowan as a giving name, I could not find much, and certainly not an interesting number of Aborigines with that name. So this all may be pure coincidence - but maybe not :)