Nobody knows, Otis. The most reasonable theory I've heard is that it originated with claim jumping (because kangaroos jump) during the California gold rush. Here's a link to the Phrase Finder, which won't give you much more than that.
Where did the saying kangaroo court come from?? I know what it means a rigged court case or hearing against u and u cannot win
This page has it's origins and all about it. Quite interesting ! Good question, Otis !