Italian isolato, from isola, from Latin insula (island): to isolate is literally to island. Insulate arrived as the engineering cousin (heat treated as water to be kept off the island); insular kept the geography's judgmental edge; peninsula, almost-island, marks the family shoreline.
Donne's 1624 meditation is the permanent counterspell: the language says isolation is island-hood, and English literature's most quoted sentence exists to deny it. The metaphor war has run four hundred years without resolution.
Insula may descend from in salo, in the swelling sea, salum being the open water. If so, every island word secretly contains the sea, and every isolated person is, by etymology, surrounded by water whether they see it or not.
Is solitude a geography before it is a feeling?