polarity n.

1550s, "from or found in the regions near the poles of the Earth," from French polaire (16c.) or directly from Medieval Latin polaris "of or pertaining to the poles," from Latin polus "an end of an axis" (see pole (n.2)). By 1816 as "of or pertaining to a pole or poles of a sphere." Meaning "directly opposite in character or tendency" is attested from 1832. Polar bear is attested from 1781.

word-forming element making abstract nouns from adjectives and meaning "condition or quality of being ______," from Middle English -ite, from Old French -ete (Modern French -ité) and directly from Latin -itatem (nominative -itas), suffix denoting state or condition, composed of -i- (from the stem or else a connective) + the common abstract suffix -tas (see -ty (2)).

Roughly, the word in -ity usually means the quality of being what the adjective describes, or concretely an instance of the quality, or collectively all the instances; & the word in -ism means the disposition, or collectively all those who feel it. [Fowler]