Ends of an axis, not a climate label
In present-day English, polar does several jobs that still share one picture. It marks what belongs to the North or South Pole, or to the high latitudes around them: ice, night, a research station, an expedition. Physicists and chemists use it for anything organized around two unlike ends, from a magnet to a molecule with a positive side and a negative side. Mathematicians speak of coordinates measured from a pole. Linguists call a yes-or-no question polar. Everyday speech reaches for polar opposites when two positions sit as far apart as a system allows. All of those uses rest on a pole: a pivot, an extremity, a pair of extremes.
The origin of the word polar is a learned sixteenth-century adjective. It did not grow out of native English stock the way north or frost did, and it did not begin as a word for snow.
A mid-century technical borrowing
English evidence for the adjective appears in the mid-1500s. The earliest dated use usually cited is 1556, in the writing of Robert Recorde, the mathematician and physician. French polaire is recorded in the same century, taken from medieval Latin polaris. How English acquired its form is not a single agreed path. Some accounts derive it from the French adjective, some from medieval or Late Latin polaris directly, and some from English pole plus the suffix -ar. One major historical dictionary treats the word as mixed: partly a Latin borrowing, partly a formation inside English. For a scholarly term of this date, those routes often ran together. Readers of Latin, translators of French scientific prose, and speakers who already knew pole could all produce the same shape.
The noun behind the adjective is older. English pole in the sense of an end of an axis had already arrived through Old French from Latin polus. That Latin noun is a borrowing of Greek pólos, which named a pivot or axis and, by a natural sky-watching step, the heavens that seemed to turn around it. Late Latin polaris meant of or pertaining to the poles. A few modern glosses render the medieval adjective as heavenly, which matches an older use of polus for the vault of the sky as well as for the ends of the world-axis. Both readings belong to one picture: the points about which the stars appear to revolve, and the places where that axis meets the Earth.
Two look-alikes must be set aside. The wooden pole, a stake or shaft, comes from Old English and Latin palus and has nothing to do with this adjective. The ethnonym Pole, a person from Poland, is another word again. Polar belongs only with the axial pole.
A Greek pivot and a Latin suffix
Greek pólos sits in a family of turning words. It is usually traced to Proto-Indo-European *kʷel-, reconstructed with the sense to revolve, move around, or dwell. In Greek, a labiovelar *kʷ often became p before certain vowels, which is why this noun begins with p rather than k. The same root, through a reduplicated form meaning circle or wheel, yields Greek kyklos and, much later, English cycle.
Latin did not inherit polus from a native Italic reflex of the root. It borrowed the Greek noun, then built an adjective with the suffix -āris. That ending is a variant of the more common -ālis, preferred after a stem that already contained l, so that a clumsy *polalis was avoided. English polar looks, on the surface, like pole plus -ar, and that analysis is fair: it matches both the Latin morphology and the English pieces. The same relational suffix appears in solar, lunar, and stellar.
Cognates of the adjective itself are mostly learned copies of the Latin form: French polaire, Italian polare, Spanish and Portuguese polar, German polar, Russian polyarnyj. More distant relatives of the underlying root, not of the adjective, include English wheel, from Old English through Germanic, and colony, cult, and cultivate, from Latin colere, to till, inhabit, or tend. Sanskrit cakra, the source of chakra, is another wheel-word from the same stock. Those cousins share turning, not ice.
From the sky to the ice, then to opposites
Early English use was astronomical first. The celestial poles are the two points in the sky around which the stars appear to wheel as the Earth turns. Writers also applied the adjective, at times, to the terrestrial poles, the two spots where that axis meets the surface. The later, familiar sense of polar regions as frozen geography grew out of that axial picture; climate was a consequence of latitude, not the original meaning of the word.
By the late eighteenth century the adjective had attached itself to animals of the high latitudes. Polar bear is recorded from 1781. By 1816 it is clearly used of a pole or poles of a sphere more generally. That same year is often given for the English phrase polar coordinates, in George Peacock’s translation of a French calculus text by Lacroix. The mathematical idea is older than the English name. Seventeenth-century writers had already located a point by a distance from a pole and an angle from an axis; Newton treated such systems among other coordinate manners, and in 1691 Jacob Bernoulli used pole and polar axis as terms.
The figurative sense, directly opposite in character or tendency, is attested from 1832. The step is almost geometric: if two poles sit at the ends of one axis, things that are polar to each other sit as far apart as the system allows. Polar opposite is now the form most speakers meet outside science. Chemistry took a parallel path. A polar molecule has ends of unlike charge, a dipole rather than a pair of ice caps. Linguists later named polar questions the yes-or-no type. None of these later senses required a new borrowing. English kept the same adjective and stretched the axis.
Keep the pivot, not the snow
The fact worth carrying away is the Greek pivot. Polar did not start as a weather word. It started as a way to talk about a turning-point in the sky. Wheel and cycle are distant relatives through a root about revolving. Ice, magnetism, and opposition are later English developments of an adjective that, in Late Latin, simply pointed at the poles. English had that adjective in place by 1556 and has been extending the axis ever since.