I guessed the same, but according to Wikipedia:
The name wallaby comes from Dharug walabi or waliba.
I'm not sure how modern anglicisation works but I assume what's given there is considered the most accurate spelling of the indigenous word. So "wallaby" isn't too far off.
Sorry what? Australia's population density is is 3.6/km², the US's is 33.6/km², almost 10 times higher. Even if you fudge it by treating the swathes of uninhabited desert as an outlier and ignoring them, you're still dealing with a raw number of people lower than the population of Texas.