Where does “Middlesex” come from?

Middlesex derives from Old English Seaxe, Old English Seaxa, and Proto-Germanic midlą meaning "middle," traced to Proto-Indo-European médʰyos with the same sense.

Middlesex (English): partly absorbed into the erstwhile County of London in 1889; finally abolished in 1965 and absorbed mainly into Greater London, the south-west corner of the county becoming Spelthorne Borough and included in Surrey. The whole county, in whatever form, had the Thames as its southern boundary

Definitions

  1. partly absorbed into the erstwhile County of London in 1889; finally abolished in 1965 and absorbed mainly into Greater London, the south-west corner of the county becoming Spelthorne Borough and included in Surrey. The whole county, in whatever form, had the Thames as its southern boundary

Ancestry of “Middlesex”, step by step

StepLanguageWordMeaning
1Old EnglishMiddelseaxanthe Middle Saxons
2Old Englishmiddelmiddle
3Proto-West Germanic*midl
4Proto-Germanicmidląmiddle
5Proto-Germanicmidjōmiddle, midst
6Proto-Indo-Europeanmédʰyosmiddle
7Proto-Indo-Europeanmedʰi-with, among; with, along
8Proto-Indo-Europeanmein the middle of, near, by, around, with
Every word from Proto-Indo-European meEvery word from Proto-Indo-European medʰi-Every word from Proto-Indo-European médʰyos
Middlesex — Etymology, Origin & Word History | Etymology Explorer