Why there are no polar bears in Antarctic?

One of my chat friend asked me this question. I found the following explanation at Frequently Asked Questions about polar bears

The distribution of all animals is a function of luck and history. Having everything you need is no guarantee of being able to reach any point on the globe once you are there because it may not be possible to get there in the first place.

Polar bears likely evolved very recently (about 200,000 years to possibly as long as 500,000 years ago) from grizzly bears somewhere off eastern Russia or the Alaskan Panhandle. They are totally dependent upon sea ice for their primary habitat for getting their food (mainly ringed seals and bearded seals). As the world's oceans never have been frozen from the north to the south, polar bears never have had the possibility to reach the Antarctic. Polar bears are strong swimmers but not strong enough to swim to the Antarctic.

Some species have wider distributions because their habitats were connected at some time in the distant past. For example, grizzly bears (also called brown bears) live in the USA, Canada, Russia, Spain, Italy and even Norway! They crossed over a land bridge between Russian and Alaska. The same is true for wolves, wolverines, lynx and many other species.

However, polar bears would really like the Antarctic. In the absence of polar bears, seals and penguins in the Antarctic are not afraid of predators (except leopard seals and killer whales). A polar bear would have a lot of fun and probably get very very fat! On the negative side, the seals and penguins would be devastated. Polar bears are really better off in the Arctic.

For more polar bear faq read: Frequently Asked Questions about polar bears

Now, here comes my question:
If there are only two poles in Earth and these bears live only in arctic region, why should they be called polar bears instead of just arctic bears?

Update:
Thanks to kathak-thestoryteller & her Dan Brown's "Deception Point" novel, I found this:
The Arctic, home of the polar bear, takes its name from the Greek arktos, meaning bear. The Antarctic, anti-arktos, is a realm devoid of bears.
http://www.ucpress.edu/books/pages/6675.html