Latin 'mediterraneus' — 'middle of the land.' Romans named the sea for being surrounded by known world.
Of or relating to the Mediterranean Sea or the countries and cultures surrounding it; (as noun) the Mediterranean Sea. Also: a type of climate characterized by hot, dry summers and mild, wet winters.
From Latin 'mediterrāneus' (inland, in the middle of land), from 'medius' (middle) + 'terra' (land, earth) + '-āneus' (adjectival suffix). The Romans called it 'Mare Mediterrāneum' — the sea in the middle of the land — because it is almost entirely enclosed by Europe, Africa, and Asia. The PIE roots are *médʰyos (middle) and *ters- (to dry, with 'terra' originally meaning 'dry land' as opposed to the sea). The compound is a Roman geographical coinage: no Greek equivalent existed in exactly this form, though the Greeks
The Greek name for the Mediterranean, 'Mesógeios Thálassa' (μεσόγειος θάλασσα), means 'the middle-earth sea' — from 'mésos' (middle) and 'gê' (earth). Tolkien's 'Middle-earth' is a translation of Old English 'middangeard' (the world between heaven and hell), which comes from the same PIE root *médʰyos that gives us 'Mediterranean.' The Mediterranean, Tolkien's Middle-earth, and the Norse Midgard are all, etymologically, the same place: the middle of the world.