1620s, "of or pertaining to a territory," from Late Latin territorialis, from territorium (see territory). In reference to British regiments, from 1881. In reference to an area defended by an animal, from 1920. Territorial waters is from 1841. Territorial army "British home defense" is from 1908. Territorial imperative "animal need to claim and defend territory" is from 1966.
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]
<a href="https://www.etymonline.com/word/territoriality">Etymology of territoriality by etymonline</a>
Harper, D. (n.d.). Etymology of territoriality. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/territoriality