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.
Entries linking to insulator
insulate v.
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.