The idea of polar suggests equal opposites. For example, the North and South Poles are at opposite ends of the planet, and both are equally glacial, or very cold, which, by the way, is another meaning of polar.
The English word polar derives from the Latin polus and the Greek polos, which means "axis." (See the connection with the North and South Poles?) The discovery of polar bears was first recorded in the mid-18th century, while the idea of "polar opposites" came about in 1832. The adjective polar is also used to describe something vitally important, an idea that came from the importance of Polaris, the North Star, which has always been a voyager’s guide.