Countering fun fact 1 for the wallaroo with my own fun fact, the word "wallaroo" is not strictly a combination of wallaby and kangaroo - it actually comes from the Dharug word for the animal, "walaru". Wallaby ("walabi") comes from the same language, hence why they sound similar, but as you mentioned kangaroo ("gangurru") comes from Guugu Yimithirr, a language from an entirely different part of Australia, so both ending with a ru/roo sound is a funny coincidence.