(5 syl.). The tin islands, generally supposed to be the Scilly Islands and Cornwall, but probably the isles in Vigo Bay are meant. It is said that the Veneti procured tin from Cornwall, and carried it to the Isles of Vigo Bay, but kept as a profound secret the place from which they obtained it. The Phoenicians were the chief customers of the Veneti.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894