GaryT: Here's a link to "Tie Me Kangaroo Down" in the DigiTrad: TIE ME KANGAROO DOWN

The verse I referred to is as follows:
Let me Abos go loose, Bruce
Let me Abos go loose
They're of no further use, Bruce
So let me Abos go loose.

I had always assumed that "letting Abos (a slur similar to the American slur 'darkies') go loose" meant freeing them from slavery upon the owner's death, as was sometimes done in the pre-Civil-War US. Am I assuming incorrectly? I searched briefly, using Google, and could not find any historical reference to Europeans ever having enslaved native Australians. But if the verse does not refer to slavery, what does it mean?