(adj.) located inland, or between two areas of land
A personal favourite etymological tale here at HH is the story of how the Aegean Sea of Greece and Turkey is so chock-full of islands that its name in Ancient Greek became our word archipelago. It literally means ‘chief sea’, as the Aegean formed the principal coastal waters of the Greek region.
But when it comes to the origin of names of seas themselves, the Mediterranean has an interesting one as well. It derives from the Latin words for ‘middle’ or ‘between’ (medius, as in medium and mediocre) and ‘land’ or ‘earth’ (terra, as in terra incognito). The Mediterranean Sea, ultimately, is the sea located between two giant expanse of land—Europe to the north, and Africa to the south.
Dating from the mid 1600s in English, the adjective mediterraneous shares the same etymology, of course, but takes its meaning in a slightly different direction. It refers to anywhere or anything entirely surrounded by land, located inland, or bounded on all or both sides by land.
Far from referring to the Mediterranean Sea, ultimately, mediterraneous typically refers to places remote from the coast, in deep isolation, or even located beneath the ground itself:
It left a sulphurous smell behind it very displeasant [sic] and offensive; which possibly, My Lord, some would conjecture to be a smack of the bituminous matter brought from the mediterraneous vaults, to which we may suppose the vehicles of those impure spirits to be nearly allied.
Joseph Glanvill, Palpable Evidence Witchcraft (1668)