When European explorers first saw these strange hopping animals they asked a native Australian, aborigine, what they were called.
He replied "kangaroo" meaning "I don't understand" your question.
The explorers thought this was the animal's name. And that's how the kangaroo got its name.

Kangaroo is the common name for any of 52 species of marsupial animals constituting the family Macropodidae, found in Australia and neighboring islands. Typical large kangaroos have sheeplike heads; large, movable ears; slender chests; and heavy hind parts. They have short front legs with five unequal digits, and long, powerful hind legs with tendons that act like springs for energy-efficient hopping.

A large kangaroo can cover a distance of 9 m (30 ft) in a single leap. The hind feet typically have four toes; the toe adjacent to the outside digit bears a long, sharp claw used in defense. The long, muscular tail is used as a support when the animal sits or walks, and for balance when it leaps. The tough hide is often covered with soft, woolly fur. Kangaroos are terrestrial
grazing animals that subsist mainly on vegetation.

Female kangaroos, like the females of other marsupials, have special abdomen pouches. The newly born young, (joey) finds its way into the pouch by following a path of fur that the mother’s tongue has moistened. The joey emerges from its mother’s pouch after six months, and
stays with her for about another three.

Kangaroos make up the family Macropodidae of the order Marsupialia. The giant kangaroo is classified as Macropus giganteus, the red kangaroo as Macropus rufus, and the wallaroo as Macropus robustus. Hare wallabies make up the genus Lagorchestes, nail-tailed wallabies the genus Onychogalea, and pademelons the genus Thylogale. The rednecked wallaby is classified as Macropus rufogriseus. Rock wallabies make up the genus Petrogale and tree kangaroos the genus Dendrolagus. The long-nosed potoroo is classified as Potorous tridactylus; the short-nosed rat kangaroo, or boodie, as Bettongia lesueur, and the musk kangaroo as Hypsiprymnodon moschatus.

Large Kangaroos are the best-known and largest species of kangaroo are the giant, or great gray, kangaroo and the red, or woolly, kangaroo. Both species reach a body length of about 1.5 m (about 5 ft), exclusive of the tail, which may be up to 1.2 m (up to 4 ft) long in the giant kangaroo. Another large species, the wallaroo, is somewhat stouter. Large kangaroos are terrestrial grazing animals that subsist chiefly on vegetation. Sheep ranchers have claimed that the animals damage grazing lands, but such overgrazing can sometimes be attributed to the sheep themselves.

Tree-kangaroos, which once descended to the ground along with other macropods, returned to the trees, perhaps simply because they found food there. The macropod blueprint for large back legs and small forearms is reversed in tree-kangaroos, and their tails are flexible. Two species survive in Australia, seven in New Guinea.

Kangaroos of smaller size, commonly called wallabies, are usually brighter in color than the large species. Many of these species are about the size of a rabbit, some so resemble rabbits that they are called hare wallabies. The nail-tailed wallabies, so called because their tails are tipped with a horny nail, and the relatively short-tailed pademelons are two other types of wallabies. The rednecked wallaby inhabits thickets, whereas the rock wallabies live in crevices in rocks. The rock wallabies are chiefly nocturnal. The only arboreal kangaroos are the small tree kangaroos, whose front legs are almost as long as their hind legs. These marsupials seem awkward in making their way either on the ground or in trees, but they prefer an arboreal habitat.

The potoroos, or rat kangaroos, are small animals that resemble jumping rats. Many of the species, although terrestrial, have a prehensile tail. Two examples are the long-nosed potoroo and the short-nosed rat kangaroo, also known as boodie or burrowing bettong.

The musk kangaroo is a ratlike wallaby living in the rain forest of northern coastal Queensland. It differs in having five toes on each hind foot and in having an almost completely naked and scaly tail. This animal may be a link between the kangaroo and the related phalanger.

Kangaroo overpopulation
Three million red and grey kangaroos are killed a year, for an industry that uses them mainly for leather, meat and pet food. The international response to this killing-campaigns in North America and Europe to place kangaroos on various lists of endangered species-never ceases to puzzle Australians. They know that a combination of the provision of well water for livestock in Australia’s arid outback and the removal of dingos has increased kangaroo numbers.

Although numbers vary greatly depending on rainfall, the long-term average population of reds and greys is about 20 million. And most marsupial biologists agree that figure is as high as it has ever been.

Perhaps some confusion over the status of the large kangaroos comes from the existence of the many other species of macropods inhabiting Australia and New Guinea--nearly half of which are considered vulnerable. At least six species are extinct. But none of the five large species open to roo shooters are in trouble. The bigger kangaroos are little affected by predators.

In national parks and the higher rainfall areas, the problem tends to be an abundance of grey kangaroos, which live in islands of woodland or bush interspersed with farmland, where they feed. Overpopulation impacts not only farm production but also the kangaroos themselves, causing increased starvation and disease.