middlesex
Middlesex (name) means the name of a county in England that no longer exists: once inland, it was partly taken into the County of London (as it then was) in 1889 and was abolished for good in 1965; most of it passed into Greater London, though the south-west corner became Spelthorne Borough and joined Surrey, and throughout, the Thames marked its southern edge.
Etymology
From Old English Middelseaxan (literally “Middle Saxons”), which stood for both Middlesex and its people.