1530s, "make into an island," from Late Latin insulatus "made like an island," from insula "island" (see isle). Sense of "place in an isolated situation, cause (someone or something) to be detached from surroundings" is from 1785. Electrical/chemical sense of "block from electricity or heat" (by interposition of a non-conductor) is from 1742. Related: Insulated; insulating.
1801, agent noun in Latin form from insulate (v.). In reference to the glass or earthenware devices to hold telegraph (later telephone) wires, from 1840s.
noun of action from insulate (v.) in its various senses. From 1767 as "a blocking from electricity or heat" (by interposition of a non-conductor). Sense of "state or action of being detached from others" is from 1798. Literal meaning "act of making (land) into an island" is from 1784; that of "state of being an island" is from 1799. The concrete sense of "insulating material" is recorded by 1870.