late 13c., ile, from Old French ile, earlier isle, from Latin insula "island," a word of uncertain origin.
Perhaps (as the Ancients guessed) from in salo "(that which is) in the (salty) sea," from ablative of salum "the open sea," related to sal "salt" (see salt (n.)). De Vaan finds this "theoretically possible as far as the phonetics go, but being 'in the sea' is not a very precise description of what an island is; furthermore, the Indo-Europeans seem to have indicated with 'island' mainly 'river islands.' ... Since no other etymology is obvious, it may well be a loanword from an unknown language." He proposes the same lost word as the source of Old Irish inis, Welsh ynys "island" and Greek nēsos "island." The -s- was restored first in French, then in English in the late 1500s.
group of volcanic islands off the northwest coast of Africa, from Portuguese madeira "wood," because the main island formerly was thickly wooded, from Latin materia "wood, matter" (see matter (n.)). As a type of fine wine of the sherry class, 1540s, from the island, where it was produced.