Well this is the report on the word, “Walleroo” in Wikipedia
“Wallaroo /wɒləˈruː/ is a common name for several species of moderately large macropods, intermediate in size between the kangaroos and the wallabies. The word "wallaroo" is from the Dharug walaru, and not a portmanteau of the words "kangaroo" and "wallaby", as is commonly assumed”
Asher