Insularity means “the state of being isolated or detached”. The word insulation can have the same meaning, though it usually refers to “a material that reduces or prevents the transmission of heat or sound or electricity”. The verb to insulate can mean both “to use insulating material” and “to isolate”.
All these words (including the word isolate) come from Latin insula, meaning island. So to be isolated or insulated essentially means “to be made into an island”. I never realized the island metaphor was so deeply ingrained into our language!
The adjective insular literally means “related to islands or islanders”, but it also means “isolated”. And the Online Etymology Dictionary says that it came to mean “narrow, prejudiced” in 1775, “from notion of being cut off from intercourse with other nations, probably with ref. to the situation of Great Britain.” Interesting, no?